No. 1 seed Andrey Rublev of Russia got past Italian Lorenzo Sonego 7-6 (3), 7-5 in the Moselle Open Round of 16 on Tuesday in Metz, France, before withdrawing from the tournament with a suspected abdominal injury.

Earlier in the day, Novak Djokovic announced he would not compete in next week's Nitto ATP Finals, the prestigious year-end event for the top eight players of the season in Turin, Italy. That meant the field of eight was finalized, with Rublev securing one of the remaining spots.

Tournament organizers announced on social media that Rublev "chose to withdraw from the tournament and travel to Turin to follow a treatment and recovery protocol, to enhance his chances of competing in the ATP Finals."

Elsewhere in the Moselle Open draw, France's Corentin Moutet upset seventh-seeded Jan-Lennard Struff of Germany 7-6 (2), 5-7, 6-3. American eighth seed Alex Michelsen is also on to the quarterfinals after saving two match points in a marathon 6-7 (4), 7-6 (3), 7-6 (8) win over home-crowd favorite Richard Gasquet of France.

In Round of 32 action, Zizou Bergs of Belgium, Yunchaokete Bu of China and Frenchmen Benjamin Bonzi and Hugo Gaston advanced.

Belgrade Open

Czech fourth seed Jiri Lehecka won 33 of 37 first-service points and absorbed his opponent's 15 aces as he hung on to defeat Croatia's Marin Cilic 6-4, 7-6 (4) in Round of 16 play in Serbia.

Next, Lehecka will face Slovakian qualifier Lukas Klein, who knocked out seventh seed Tomas Martin Etcheverry of Argentina 6-4, 7-6 (6).

Serbians Hamad Medjedovic and Laslo Djere won in straight sets, as did Roman Safiullin of Russia. Medjedovic is already on to the quarterfinals while the others won their first-round matches.

--Field Level Media