For brothers Alexander and Mischa Zverev, this was, in many ways, just like any other day on the professional tennis tour: They warmed up together at a tournament.

The difference on Thursday at the Citi Open, where Alexander is the defending champion and seeded No. 1. For the first time after one of those practice sessions, the two Zverevs faced each other in an ATP main-draw match.Seems safe to say Alexander has never hugged an opponent quite the way he did No. 15 seed Mischa after beating his older sibling 6-3, 7-5 to reach the quarterfinals at the hard-court tuneup for the U.S. Open.

Alexander is ranked No. 3, Mischa No. 42. Alexander is a righty, Mischa a lefty. Alexander is 6-foot-6 (1.98) and prefers baseline exchanges, while Mischa is 6-foot-3 (1.91 meters) and likes to go to the net.

In Friday’s quarterfinals, he’ll play No. 7 Kei Nishikori, who defeated No. 9 Denis Shapovalov 7-6 (1), 6-3, and No. 3 David Goffin faces No. 10 Stefanos Tsitsipas.