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Roger Federer will drop from the Top 5 of the ATP Rankings on 28 January.

Rankings Update: Federer To Drop From Top 5; Zverev To Rise To No. 3 Despite Loss

Tsitsipas has opportunity to reach the Top 10

Editor's Note: This story, originally published on 19 January, was updated on 21 January.

It took one day in the second week of the Australian Open to create a major shake-up when the new ATP Rankings are released on 28 January.

ATPTour.com looks at the most glaring changes that will occur based on the results thus far in Melbourne, and what could happen throughout during the rest of the tournament.

Federer To Fall Out Of Top 5, As Low As No. 7
Federer suffered a stunning loss against reigning Next Gen ATP Finals champion Stefanos Tsitsipas in the fourth round. Since Federer was defending 2,000 points, the pressure was on for the six-time champion to make another deep run in Melbourne. The 37-year-old will fall outside the Top 5 of the ATP Rankings for the first time since 20 March 2017.

A fourth-round showing will leave Federer with 4,600 points. Alexander Zverev was already guaranteed to pass the Swiss for the No. 3 spot before his loss. World No. 5 Juan Martin del Potro, who did not compete at the Australian Open, is locked in at 5,060 points, and World No. 6 Kevin Anderson, who lost in the second round, will have 4,845 points when the new ATP Rankings are released on 28 January.

The lowest Federer can fall after the tournament at this point is No. 7. If Kei Nishikori reaches the final, he will have 4,950 points, and could then add 800 more should he lift his maiden Grand Slam title.No other player could surpass Federer's point total.

Zverev Guaranteed To Reach No. 3
Despite his fourth-round loss to Milos Raonic Monday, Alexander Zverev is guaranteed to match his career-high of No. 3 in the ATP Rankings. Since the German reached the third round last year, he only had 90 points to defend, whereas World No. 3 Federer, as last year's champion, was defending 2,000 points, and lost in the fourth round.

Round-By-Round ATP Rankings Projection

 Player  Australian Open Champion  Finalist  SF  QF  R16
 Rafael Nadal  9,120  8,320  7,840  7,480  7,300
 Alexander Zverev  8,295  -  - -  6,475

Watch Zverev's Road To The 2018 Nitto ATP Finals Title:

Tsitsipas Could Crack The Top 10
Tsitsipas stunned six-time champion Federer on Sunday to reach his first major quarter-final. The reigning Next Gen ATP Finals champion Tsitsipas, who advanced to the fourth round of a Slam for the first time at Wimbledon last year, now faces Bautista Agut to reach the last four. If he should go on a dream run and claim the title in Melbourne, Tsitsipas would soar into the Top 10 of the ATP Rankings. A victory would send him to at least No. 8, while a Nishikori fourth-round loss would allow him to climb to No. 7.

How would the Greek make such an ascent? Based on Fabio Fognini (2,225 points) and Kyle Edmund’s (1,440) early losses, Tsitsipas is currently projected to reach a career-best No. 13 in the ATP Rankings. A title would give Tsitsipas — who was only defending 10 points from a 2018 first-round loss — 4,085 points on 28 January. That would put him past eliminated players Dominic Thiem (3,960), John Isner (3,155), Karen Khachanov (2,880), Fognini and Edmund, all of whom are currently ranked ahead of him.

With Cilic already eliminated (3,140), he would surpass the Croat as well. While Tsitsipas could potentially face Coric in the final, a championship-match appearance would give Coric 3,625 points, which would be less than Tsitsipas’ 4,085.

Keep in mind that during such a run, Tsitsipas would potentially have to face second seed Nadal in the semi-finals and World No. 1 Djokovic for the title.

Tsitsipas' Round-By-Round ATP Rankings Projection

 Australian Open Champion  Finalist  SF  QF
 4,085  3,285  2,805  2,445

Cilic Could Drop From The Top 10
There could be a lot of movement in the ATP Rankings after Marin Cilic lost to Doha champion Roberto Bautista Agut in the fourth round. That defeat puts the Croat in danger of falling outside of the Top 10.

Cilic, who was defending 1,200 points from his runner-up showing in 2018, will have 3,140 points on 28 January. So at maximum, he will be World No. 10, his lowest standing since 31 October 2016. Borna Coric can now crack the Top 10 for the first time with a trip to at least the semi-finals. If #NextGenATP Greek Stefanos Tsitsipas makes the final, he would also pass Cilic.

The following players would also surpass Cilic’s 3,140 points if they were to win their maiden Grand Slam trophy: Milos Raonic, Daniil Medvedev, Pablo Carreno Busta, Roberto Bautista Agut and Lucas Pouille.

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