American Frances Tiafoe, 20, stuns Kevin Anderson at Australian Open

MELBOURNE, Australia — Frances Tiafoe rolled up his sleeve, flexed and slapped his biceps muscle five times to celebrate the biggest victory of his career, a 4-6, 6-4, 6-4, 7-5 comeback against two-time Grand Slam finalist and No. 5 seed Kevin Anderson in the Australian Open’s second round.

Tiafoe, 20, trailed by a set and 3-0 in the second Wednesday before turning the match around as Anderson’s big serve slowed down because of problems with his right arm. Anderson was repeatedly visited by a trainer during changeovers and he lost about 5 mph on his first serves as the match progressed.

Anderson was the runner-up at Wimbledon last year and at the U.S.