NEW YORK, Sept 3 (Reuters) - German Angelique Kerber triumphed in the battle of the former champions on Friday, downing Sloane Stephens 5-7 6-2 6-3 to reach the fourth round of the U.S. Open for the first time since 2018. The 16th-seeded hadn"t taken a set off of Stephens in their last five meetings and it looked as though history would repeat itself as Kerber committed 18 unforced errors and a double fault in the first set. But the 2016 champion wrested the momentum from the American, cleaning up her game in the second set, where she never faced a break point and won the final five games in Louis Armstrong Stadium. She put up a strong defensive performance as the 2017 Flushing Meadows winner lobbed 13 forehand winners in the third set, fending off three break points in the sixth game and converting on break point in the next, helped by a double fault from Stephens. She let out a cheer as she booked her second consecutive trip to the fourth round at the U.S. Open and gave credit to Stephens" impressive play. "To play against Sloane - it"s always a tough match," said Kerber. "I knew before that I have to play my best tennis and also after the first set I was just trying to stay in the match."