Frenchman Arthur Fils topped Italian Luca Nardi in their round-robin opener at the Next Gen ATP Finals on Tuesday in Jeddah, Saudi Arabia.

The event format calls for best-of-five play, with four games winning the set. Eight players are divided into two groups -- red and green.

Fils needed all five sets to defeat Nardi, taking a 2-4, 4-3 (6), 4-2, 1-4, 4-2 victory in Green Group play.

Another Italian, Flavio Cobolli, moved to 1-0 in the Green Group, beating Dominic Stricker of Switzerland 4-2, 3-4 (7), 4-1, 4-2.

In the Red Group, Serbia's Hamad Medjedovic and American Alex Michelsen played the second five-set match of day in a Red Group pairing. Medjedovic squandered a two-set lead but emerged with a 4-2, 4-3 (3), 3-4 (3), 3-4 (5), 4-3 (4) victory.

France's Luca van Assche knocked off Abedallah Shelbayh of Jordan 4-3 (5), 3-4 (5), 4-1, 4-1, also in the Red Group.

The ATP Next Gen Finals are the season-ending event for the top-ranked male players 21 and under.

Carlos Alcaraz of Spain and Holger Rune on Denmark both qualified by age, but they also qualified for the overall ATP Finals and are not in Jeddah.

Ben Shelton (medical) and Lorenzo Musetti (personal) both withdrew.

After the round-robin stage, the tournament moves to the semifinals.

--Field Level Media