MELBOURNE, Australia — Frances Tiafoe celebrated his 21st birthday in style on Sunday with a 7-5 7-6 (6), 6-7 (1), 7-5 win over No. 20-seeded Grigor Dimitrov to advance to his first Grand Slam quarterfinal.

Tiafoe, who received treatment on his right forearm at the end of the third set, broke Dimitrov’s serve in the 11th game of the fourth then held serve to end the 3-hour, 39-minute match.

In typical style, Tiafoe took off his T-shirt, flexed his right bicep and waved to the crowd. Then he sat in his chair and covered his head with a towel.

It’s a big turnaround for the American at the Australian Open. He lost all three singles matches at the exhibition Hopman Cup three weeks ago, then was beaten in the first round at the Sydney International.

At Melbourne Park, he has beaten No. 5 Kevin Anderson and veteran Andeas Seppi.

Tiafoe will next play second-seeded Rafael Nadal, a 6-0, 6-1, 7-6 (7) winner over Tomas Berdych.