Jannik Sinner, the 18-year-old who is the youngest player in the Top 100, wins the Next Gen ATP Finals.

Jannik Sinner was ranked outside the Top 500 to start 2019. On Sunday, he won the Next Gen ATP Finals title.

Jannik Sinner becomes the first Italian to win the Next Gen ATP Finals in Milan.

At No. 95 in the ATP Rankings, Jannik Sinner is the lowest-ranked player to win the Next Gen ATP Finals.

Alex de Minaur leaves Milan with an 8-2 record after his second consecutive runner-up finish.

Jannik Sinner, who watched the 2018 Next Gen ATP Finals from the stands, triumphs in Milan.

Jannik Sinner gives his coach, Riccardo Piatti, an incredible birthday present by reaching the championship match at the Next Gen ATP Finals.

Jannik Sinner wins 12 of the last 17 games to defeat Miomir Kecmanovic at the Next Gen ATP Finals.

Alex de Minaur improves to 8-1 at the Next Gen ATP Finals.

Alex de Minaur improves to 8-1 at the Next Gen ATP Finals after reaching the championship match for the second straight year.

Frances Tiafoe looks for revenge against Alex de Minaur in their semi-final clash at the Next Gen ATP Finals.

Miomir Kecmanovic has jumped more than 70 spots in the ATP Rankings this year.

Alex de Minaur looks to reach the championship match at the Next Gen ATP Finals for the second consecutive year.

Frances Tiafoe didn't drop serve en route to defeating Mikael Ymer at the Next Gen ATP Finals.

Ugo Humbert scores his maiden victory at the Next Gen ATP Finals against Jannik Sinner.

Frances Tiafoe breaks Mikael Ymer three times to advance out of Group B at the Next Gen ATP Finals.

Miomir Kecmanovic didn't face a break point in his win on Thursday against Alejandro Davidovich Fokina.

Alex de Minaur moves to 6-0 in round-robin play in his two appearances at the Next Gen ATP Finals.

Alejandro Davidovich Fokina is fired up to end his season on a high at the Next Gen ATP Finals.

Jannik Sinner's 56-minute win over Mikael Ymer is the second-fastest in tournament history.

Jannik Sinner records the most dominant scoreline in tournament history with his win over Mikael Ymer.

Frances Tiafoe keeps himself in contention to advance out of Group B with a win over Ugo Humbert.

Miomir Kecmanovic looks to advance out of Group A at the Next Gen ATP Finals.

Alex de Minaur moves to 2-0 in Group A on Wednesday at the Next Gen ATP Finals in Milan.

Alex de Minaur takes the lead in Group A after his win on Wednesday over Miomir Kecmanovic.

Norway's Casper Ruud will look to advance to the Next Gen ATP Finals semi-finals on Thursday.

Casper Ruud moves to 1-1 in Group A on Day 2 at the Next Gen ATP Finals.

Mikael Ymer has thrived off support from Stefan Edberg and other Swedish tennis legends.

Jannik Sinner becomes the first Italian to win a match at the Next Gen ATP Finals.

Mikael Ymer gets off to a good start in Milan with a four-set win against Ugo Humbert.

Mikael Ymer continues his success indoors with his maiden win at the Next Gen ATP Finals.

Alex de Minaur will look to return to the Next Gen ATP Finals title match this week in Milan.

Alex de Minaur remains unbeaten (4-0) in round-robin play at the Next Gen ATP Finals.

Miomir Kecmanovic didn't drop serve to win his debut match at the Next Gen ATP Finals.

Alejandro Davidovich Fokina puts the finishing touches on his Next Gen ATP Finals preparations.

Alex de Minaur has posted a 14-5 record since the start of the US Open.

The third edition of the Next Gen ATP Finals will take place from 5-9 November at Allianz Cloud, Milan.

(L to R): Mikael Ymer, Jannik Sinner, Alejandro Davidovich Fokina, Frances Tiafoe, Ugo Humbert, Miomir Kecmanovic and Casper Ruud attend the draw party for the 2019 Next Gen ATP Finals.

Jannik Sinner will make his debut at the Next Gen ATP Finals this year in Milan.