LONDON—Having already qualified for the semifinals, Rafael Nadal guaranteed himself the theoretically easier route through them by finishing at top of his group—ensuring that he will play the runner-up of Group B (either Roger Federer or Juan Martin del Potro) on Sunday, reserving any potential meeting with Novak Djokovic for the Monday final—all by the simple expedient of winning a set against Tomas Berdych. Never one to do things by halves, he won the match too, recovering from a disastrous second set for a 6-4, 1-6, 6-3 victory.

Under the circumstances, Nadal can be forgiven for abruptly vacating the court, mentally if not physically, after clinching a toughly-contested first set. He came out firing and snatched an initial break before Berdych had quite succeeded in attuning himself to events, then hung on to it grimly for the next 40 minutes.

After steadying himself with a tough hold for 1-2, Berdych began to produce some typically beautiful ball-striking—with the inevitable sprinkling of equally typical unforced errors. It took highly effective serving from Nadal—he won 88 percent points behind his first serve in that set—and constant injections of pace on the backhand, as well as a willingness to find the sharper angles on that wing, to keep Berdych at bay and under pressure.

There’s no doubt that Nadal’s exploits this year have earned him a vacation, and there are worse times to take one than when you have just sealed a fine set and won your group. Whether it was a planned relaxation or a spontaneous implosion, Nadal celebrated his first-set victory by producing a stretch of five deplorable games in which he won just four points. Berdych, meanwhile, suddenly able to breathe and play without facing a relentless barrage, started to flow from one winner to the next, punctuating them with searing aces which drew gasps from the pro-Nadal crowd.

It took just 29 minutes for the Czech to serve out a 6-1 set, but there were signs of Nadal stirring from his stupor towards the end. Berdych’s best chance to take the lead in the third set came in the first game, when an utterly bizarre mistimed backhand from Nadal got him to deuce, but he wasted that opportunity with a careless forehand in the net. He never got quite so close to breaking Nadal again, as the world No. 1 began to look increasingly like his first-set incarnation. Most importantly, he got a little bite and utility back on his serve and started to run Berdych side-to-side behind it, seeking the opportunity for a winning forehand down the line.

It tilted the match back in his favor, and when Berdych opened his service game at 3-4 with a routine error and a double fault, Nadal capitalized, giving himself three break chances with a forehand winner before Berdych double-faulted again. Serving it out to love, on match point he responded to a magnificent Berdych backhand with a winner that didn’t so much pass Berdych as seem to go straight through him. It’s the Berdych-Nadal history writ small: Taking the best the big man can produce and returning it with interest. It dismissed Berdych from the tournament and put Wawrinka in the semifinals.