NEW YORK - Fifth-seeded Flavio Cobolli rallied from two sets down to beat Francisco Comesana at the US Open on Sept 1, where top-seeded Alexander Zverev and No. 4 Coco Gauff were finally slated for first-round action.

Italy’s Cobolli, runner-up to Zverev at the French Open, shook off an erratic start to triumph 3-6, 2-6, 6-3, 6-4, 6-4, dropping to his knees and raising his arms in celebration after closing out the four-hour, 13-minute marathon.

“In a Grand Slam it’s never done,” Cobolli said. “You have to fight to the last point.”

Cobolli rallied from an early break in the fifth set, breaking back to pull level, breaking again for a 5-4 lead and sealing the triumph in the next game with a blistering forehand volley.

The Italian had been flailing in the first two sets against his 119th-ranked opponent, but he seemed to have turned a corner when he fought off two break points early in the third and broke Comesana with a powerful forehand for a 3-1 lead.

“After two sets down I went to the toilet and I changed everything because maybe (it was) unlucky,” he told the crowd in an on-court interview. “So I changed everything – and maybe it works.”

Cobolli saved all eight break points he faced in the third set, including two in the final game, and roared to a 4-0 lead on the way to taking the fourth.

In the time it took Cobolli and Comesana to battle it out on the covered Louis Armstrong stadium, Americans Madison Keys and Taylor Fritz both posted wins on Arthur Ashe Stadium.

Rybakina races through

Meanwhile, players scheduled on outside courts waited through rain that delayed the start of play for almost four hours.

World number two Elena Rybakina, whose match on Grandstand court was one of those delayed by rain, raced past 17-year-old US wild card Thea Frodin 6-3, 6-2.

Rybakina, who claimed her second Grand Slam title at the Australia...