Novak Djokovic works on his 'floss' dance after visiting LIVE with Kelly and Ryan.

Novak Djokovic poses with his US Open trophy during his visit to the TODAY show.

Three-time US Open champion Novak Djokovic was excited to see the crocodile at the American Museum of Natural History.

Novak Djokovic visits the American Museum of Natural History during a media tour the day after his 2018 US Open victory.

Juan Martin Del Potro's motivation is high despite falling in straight sets to Novak Djokovic in Sunday's US Open final.

Novak Djokovic is now 34-4 since a 6-6 start to his 2018 season.

Novak Djokovic embraces Juan Martin Del Potro after claiming his fourth US Open title on Sunday.

Novak Djokovic celebrates his third US Open title following his straight-sets victory against Juan Martin del Potro.

Novak Djokovic equals Pete Sampras' tally of 14 Grand Slam titles after lifting his third US Open title on Sunday.

Novak Djokovic celebrates his third US Open title.

The flag of the United States of America is displayed before the US Open final.

Novak Djokovic is aiming to win his third US Open title.

Juan Martin del Potro and Novak Djokovic are meeting for the 19th time in their FedEx ATP Head2Head series (Djokovic leads 14-4).

Novak Djokovic is aiming to lift his third US Open title and join Pete Sampras on 14 Grand Slam titles.

Novak Djokovic has won his past 13 sets at the US Open heading into Sunday's final against Juan Martin del Potro.

Juan Martin del Potro will face Novak Djokovic, for the 19th time in their FedEx ATP Head2Head series, in the US Open final on Sunday.

Jamie Murray and Bethanie Mattek-Sands beat Nikola Mektic and Alicja Rosolska to win the US Open mixed doubles title on Saturday.

Mike Bryan and Jack Sock won their second straight Grand Slam title at the US Open.

Novak Djokovic is bidding for a third US Open crown.

Novak Djokovic is bidding for a third US Open crown.

Rafael Nadal departs Arthur Ashe Stadium after retiring from his US Open semi-final against Juan Martin del Potro.

Jack Sock and Mike Bryan drop just one set en route to claiming the 2018 US Open title.

Mike Bryan and Jack Sock win their second consecutive Grand Slam championship, triumphing at the US Open.

Mike Bryan and Jack Sock will bid for their second straight Grand Slam doubles title together after holding off Colombians Robert Farah and Juan Sebastian Cabal at the US Open.

John Millman heads off court at 2-2 in the second set, as Novak Djokovic takes his own break in humid conditions at the US Open.

Novak Djokovic celebrates beating John Millman on Wednesday night for a place in the US Open semi-finals.

Two-time former champion Novak Djokovic strikes a backhand volley past John Millman on Wednesday in their US Open quarter-final.

John Millman congratulates Novak Djokovic on his quarter-final victory at the US Open on Wednesday night.

Novak Djokovic reaches his 11th US Open semi-final by defeating Aussie John Millman on Wednesday evening.

Marin Cilic landed 57 winners in his five-set loss to Kei Nishikori at the US Open on Wednesday.

Kei Nishikori defeats Marin Cilic in five sets at the US Open on Wednesday.

Mike Bryan and Jack Sock defeat Maximo Gonzalez and Nicolas Jarry in straight sets at the US Open on Wednesday.

Kei Nishikori owns a 3-0 record in US Open quarter-finals.

Rafael Nadal embraces Dominic Thiem on Wednesday morning at the end of their US Open quarter-final.

World No. 1 and three-time champion Rafael Nadal celebrates beating Dominic Thiem after their epic five-set US Open quarter-final win.

Rafael Nadal commiserates with Dominic Thiem at 2:04 a.m. on Wednesday at the end of their US Open quarter-final.

Dominic Thiem said, “It’s going to be stuck in my mind forever" following his epic five-set loss to Rafael Nadal at the US Open.

Rafael Nadal celebrates reaching the US Open semi-finals with victory over Dominic Thiem in a match that finished at 2:04 a.m. on Wednesday.

After the birth of his first child, US Open quarter-finalist John Isner will focus on qualifying for the Nitto ATP Finals in November.

Robert Farah and Juan Sebastian Cabal defeat Rohan Bopanna and Edouard Roger-Vasselin at the US Open on Tuesday.

Juan Martin del Potro defeats John Isner in four sets at the US Open on Tuesday.

John Isner is aiming to become the first American since Andy Roddick in 2006 to reach the US Open semi-finals.

Juan Martin del Potro is bidding to reach his third US Open semi-final on Tuesday.

John Millman celebrates beating one of his heroes, Roger Federer, in the early hours of Tuesday morning at the US Open.

John Millman shakes Roger Federer's hand after his stunning fourth-round victory at the US Open on Monday night.

Roger Federer suffers a shock fourth-round exit to John Millman in the early hours of Tuesday morning at the US Open.

Bruno Soares and Jamie Murray extend their winning streak to seven with a win over Matwe Middelkoop and Robin Haase at the US Open.

Marin Cilic sends No. 10 seed David Goffin packing in the fourth round of the US Open on Monday.

Novak Djokovic owns an 11-0 record in US Open fourth-round matches.

Kei Nishikori books his place in the US Open quarter-finals for the third time after a straight sets win over Philipp Kohlschreiber on Monday.

Juan Martin del Potro advances to the quarter-finals of the US Open for the third consecutive year.

In a match featuring six breaks of serve, John Isner dismisses Milos Raonic in five sets.

Juan Martin del Potro has yet to lose a set through four rounds at the 2018 US Open.

Lukasz Kubot (front) and Marcelo Melo see off Roland-Garros champions Pierre-Hugues Herbert and Nicolas Mahut to reach the US Open quarter-finals.

Joao Sousa will get a shot at two-time champion Novak Djokovic inside Arthur Ashe Stadium, where he played his first FedEx ATP Head2Head match against the Serbian five years ago.

John Isner advances to his second US Open quarter-final with a five-set win against former World No. 3 Milos Raonic.

Novak Djokovic wins 65 per cent of second-serve return points in three-set win over Richard Gasquet at the US Open on Saturday.

Dominic Thiem hits 41 winners in three-set victory over Kevin Anderson at the US Open on Sunday.

Rafael Nadal will face Dominic Thiem for the 11th time in their FedEx ATP Head2Head series (7-3) at the US Open on Tuesday.

Rafael Nadal beats Nikoloz Basilashvili in four sets to reach his eighth US Open quarter-final on Sunday.

Dominic Thiem defeats Kevin Anderson in three sets to reach his first US Open quarter-final on Sunday.

#NextGenATP Aussie Alex de Minaur falls just short of reaching the fourth round of a Grand Slam for the first time.

Marin Cilic, the 2014 US Open champion, comes from two sets down to defeat #NextGenATP Alex de Minaur in five sets.

Novak Djokovic extends his FedEx ATP Head2Head lead against Richard Gasquet to 13-1.

Aussie John Millman reaches the second week of a Grand Slam for the first time by beating Mikhail Kukushkin on Saturday.

Philipp Kohlschreiber defeats No. 4 seed Alexander Zverev to reach the fourth round of the US Open for the fifth time in seven years.

Philipp Kohlschreiber defeats No. 4 seed Alexander Zverev to reach the fourth round of the US Open for the fifth time in seven years.

Roger Federer shovels a shot around the netpost at 3-3 in the third set of his third-round match against Nick Kyrgios on Saturday.

Mike Bryan and Jack Sock defeat Mackenzie McDonald and Yoshihito Nishioka in 59 minutes to reach the US Open third round on Saturday.

Roger Federer improves his FedEx ATP Head2Head series lead to 3-1 against Nick Kyrgios with a victory in the third round of the US Open.

Nick Kyrgios reacts to an around-the-netpost shot by Roger Federer in the third set of their third-round match at the US Open.

Roger Federer leads Nick Kyrgios 2-1 in their FedEx ATP Head2Head series.

Juan Martin del Potro is cruising into the second week at the US Open.

Juan Martin del Potro has not dropped a set thus far in New York.

Milos Raonic is not broken en route to victory against 2016 US Open champion Stan Wawrinka in the third round.

Milos Raonic posts his second FedEX ATP Head2Head victory in six meetings with 2016 champion Stan Wawrinka at Flushing Meadows.

Milos Raonic posts his second FedEX ATP Head2Head victory in six meetings with 2016 champion Stan Wawrinka at Flushing Meadows.

Karen Khachanov battled for four hours and 23 minutes before falling short against World No. 1 Rafael Nadal.

Rafael Nadal battles into the Round of 16 at the US Open.

Kevin Anderson defeats #NextGenATP Canadian Denis Shapovalov to reach the US Open Round of 16 on Friday.

Denis Shapovalov is aiming to reach the US Open Round of 16 for the second straight year.

Kevin Anderson is bidding to reach the Round of 16 at the US Open for the third time in four years.

Rafael Nadal survives a stern test from Karen Khachanov at the US Open.

Karen Khachanov is bidding to reach a third straight Grand Slam fourth round.

Diego Schwartzman sets a 3R clash against Kei Nishikori at the US Open.

Novak Djokovic defeats Tennys Sandgren for the second time in two Grand Slams to reach the third round at the US Open.

Jamie Murray and Bruno Soares ease past Guido Pella and Albert Ramos-Vinolas to reach the US Open second round.

Alex de Minaur is streaking towards the second week at the US Open.

Julien Benneteau plays his final professional match at the 2018 US Open.

John Millman reaches the third round at the US Open for the second straight year.

Alexander Zverev defeats Nicolas Mahut in straight sets to reach the US Open third round on Thursday.

Alexander Zverev leads the ATP World Tour with 44 tour-level victories this season.

World No. 1 Rafael Nadal wins his ninth consecutive match at the US Open, defeating Vasek Pospisil on Wednesday evening.

Andy Murray, who won the US Open in 2012, hit 35 winners to 46 unforced errors in his loss against Fernando Verdasco on Wednesday.

Denis Shapovalov survives in five sets to reach the US Open third round.

John Isner survives in five sets to reach the third round at the US Open.

Joao Sousa and Leonardo Mayer pull off the first-round upset of top seeds Oliver Marach and Mate Pavic at the US Open.

Kevin Anderson reaches the third round of the US Open for the fifth consecutive year.

Fernando Verdasco earns a gritty four-set win over Andy Murray at the US Open.

Juan Martin del Potro blasts into the third round at the US Open without dropping a set.

Dominic Thiem extends his FedEx ATP Head2Head series lead against Steve Johnson to 3-1 with a victory at the US Open.

Stan Wawrinka extends his US Open win streak to nine straight, advancing to the third round.

Diego Schwartzman breezes into the second round of the US Open with a straight sets win over Malek Jaziri on Tuesday.

David Ferrer is heading into retirement following an illustrious career on the ATP World Tour.

Five-time US Open champion Roger Federer remains undefeated in first-round matches at the US Open, beating Yoshihito Nishioka Tuesday.

Nick Kyrgios advances to the second round of the US Open. He could face Roger Federer in the third round.

Roger Federer reaches for a smash on his way past Japan's Yoshihito Nishioka in the opening round of the US Open.

Kei Nishikori is bidding to reach the US Open final for a second time.

Alexander Zverev defeats Peter Polansky in straight sets at the US Open on Tuesday.

Richard Gasquet moves into the US Open second round.

Novak Djokovic celebrates a steamy first-round victory over Marton Fucsovics at the US Open.

Marin Cilic records his 30th US Open victory on Tuesday.

Denis Shapovalov will meet Italian veteran Andreas Seppi in the second round of the US Open.

Rafael Nadal advances to the second round of the US Open for the 14th time.

Former champion Juan Martin del Potro secures a second-round berth at the US Open.

Steve Johnson books his spot in the second round of the US Open.

Gilles Muller plays his final match 13 years after defeating Andy Roddick at the US Open.

Florian Mayer loses to Borna Coric in the last match of his career.

Ugo Humbert reaches the US Open second round in his Grand Slam debut.

Taylor Fritz registers the first two-set comeback of his career to reach the second round at the US Open.

John Isner scores his 25th match win at the US Open.

Andy Murray remains undefeated in his opening matches of the US Open, defeating James Duckworth.

Stan Wawrinka defeats Grigor Dimitrov for the fourth time in eight FedEx ATP Head2Head meetings at the US Open on Monday.

Rafael Nadal will meet countryman David Ferrer in the US Open first round on Monday night.

Ivan Lendl, who has coached former World No. 1 Andy Murray, is now a part of World No. 4 Alexander Zverev's team.

Mitchell Krueger celebrates his first Grand Slam main draw appearance after battling through qualifying.

Felix Auger-Aliassime is all smiles after qualifying for his first Grand Slam main draw.

Casper Ruud qualifies for the US Open, his third successful Grand Slam qualifying bid of 2018.

Andy Murray begins his 2018 US Open campaign against Aussie James Duckworth.

Roger Federer will begin his 2018 US Open campaign against Japanese Yoshihito Nishioka.

Felix Auger-Aliassime reaches the final round of qualifying at the US Open.

Mitchell Krueger celebrates a second round qualifying victory at the US Open.

Pedro Martinez celebrates a comeback win in the second round of US Open qualifying.

Alexander Zverev, the No. 4 seed at the US Open, will face a qualifier in the first round. This is his first tournament with Ivan Lendl on his coaching staff.

World No. 1 and defending champion Rafael Nadal faces compatriot David Ferrer in the first round of the 2018 US Open.

Novak Djokovic will begin his 2018 US Open campaign against Hungarian Marton Fucsovics.

Felix Auger-Aliassime moves into the second round of US Open qualifying.

Miomir Kecmanovic advances to the second round of US Open qualifying.

Sebastian Korda celebrates his first Grand Slam qualifying victory at the US Open.

Christian Harrison rallies for a first-round victory at US Open qualifying.

Roger Federer is bidding for a sixth US Open title.