PARIS (Reuters) - American teenager Coco Gauff was knocked out in the second round of the French Open after losing her way following a solid opening set in a 4-6 6-2 7-5 defeat to Italian qualifier Martina Trevisan on Wednesday. On the day 23-times Grand Slam singles champion Serena Williams withdrew with an Achilles injury, Gauff was looking to keep the Stars and Stripes flying but she eventually flagged, serving two double faults in the last game. The 16-year-old, the youngest player in the main draw who reached the fourth round of the Australian Open this year as well as at Wimbledon in 2019, was in control before allowing her opponent into the contest. Trevisan then took full advantage to set up a meeting with Greek 20th seed Maria Sakkari. Another American teenager, Amanda Anisimova, advanced into the third round on Wednesday.