When it comes to returning serve, the consensus is that the farther back you stand, the worse off you are. And that’s how it looked in the first set today for Juan Martin del Potro, as he put himself up against the back wall at the Citi Open in a seemingly futile attempt to get John Isner’s serve in play. The sleepy and sluggish Del Potro, who was barely in camera range, appeared to be in full retreat, ready to wave the white flag. He had finished his semifinal win over Tommy Haas in the wee hours the night before, and he speedily lost the first set this afternoon, 6-3. The question was whether he would recover before the hot-hitting Isner blasted him off the court entirely.

As the second set progressed, though, it became clear del Potro’s return position near the Potomac was only a tactical retreat, and a smart one at that. It isn’t always a bad move to give up ground, especially against a guy who relies on aces and service winners as much as Isner does. Suddenly those unreturnable bombs become much more returnable, and there’s no target for body serves, either—Isner hit 29 aces in his semifinal win over Dmitry Tursunov; today he finished with six. He also had four double faults, and by the middle of the second set, del Potro had found his groove from the hinterlands. Isner would end up winning just eight of 22 second serve points for the match, as well as a relatively low 30 of 43 on first serves. Normally a hard man to break, Isner surrendered his serve four times, including three straight at the end of the second and start of the third sets.

Del Potro slowly found his rhythm on his own serve as well. In the first set, he was hitting them 110 m.p.h; by the third, he was up in the high 120s. Over that period, he also turned things around from the ground. Isner began by backing him up with heavy forehands, but by the end del Potro was in total control when the rallies began. He hit his forehand for winners to both corners, and was just as impressive with his dipping backhand pass.

Isner had won eight straight matches, but he began the day saying that del Potro would be step up in class. He was, unfortunately for him, correct. Del Potro’s surprisingly quick, 1 hour, 28 minute, 3-6, 6-1, 6-2 win was never in doubt after the first set. The Argentine excelled on the big points all week and won his third straight title in Washington, D.C. The last two times he won there, in 2008 and 2009, he kickstarted strong summer runs that lasted through the U.S. Open—in ’09, it took him all the way to the title in New York. Would you be surprised if it happened again?