This part might cause some nightmares before Sunday: Roddick is 2-18 against Federer, including losses in the 2004 and 2005 Wimbledon finals, as well as the 2006 U.S. Open final.

“I’ve had plenty of time to study his game, to understand his game,” Federer said. “He’s always played me also quite differently every single time.”

Then again, Roddick was 2-6 previously against Murray, who was trying to become the first British man to reach the Wimbledon final since the 1930s and, of course, received plenty of partisan support from the 15,000 or so spectators.

Roddick joked beforehand he’d be pretending that all those shouts of “Come on, Andy!” were for him, but he was outsmarted: Instead of the usual first-name cheers, the crowd yelled support for their man “Murray!”

Didn’t matter. Roddick was too good on the most important points and that made the difference on a day Murray compiled more aces (25-21), more winners (76-64) and fewer unforced errors (20-24). Roddick won far more points at the net, 48-15, and put in a far higher percentage of first serves, 75-52, while hitting much harder than Murray, reaching a tournament-high 143 mph.

“If he serves like that,” Murray said, “he’s got a chance against anyone.”

There was only one break point in the first set, and it came with Murray serving while trailing 5-4. Murray went ahead 30-love, but Roddick took the next four points, showing off some of the newfound versatility in his game. He got to break point with a drop-shot winner on a 10-stroke exchange. And he ended the set with a booming backhand down the line that forced Murray into a forehand error on the point’s 17th stroke.

The stands were close to silent, and it was clear Murray needed to do something to get the fans — and himself — going. He did just that, breaking Roddick at love to open the second set, then holding with the help of three aces in a row to go up 2-0.

After serving out that set, Murray was on the verge of beginning the third the exact same way. But Roddick saved three break points to hold for 1-0.

“You’re probably not going to get out of a love-40 hole too often against a guy who returns like him,” Roddick said. “So that was definitely key.”

Roddick broke to 3-1, and at 5-2 was two points away from taking the third set. But Murray eventually broke back and, in the tiebreaker, he held a set point at 6-5. On a 13-stroke exchange, Roddick misplayed a forehand volley in such a way that it turned into a winner.

“He apologized,” Murray said.

Moments later, Murray shanked one forehand long, then dumped a passing try into the net, and Roddick owned the lead and momentum. Less than an hour later, Roddick owned the match, improving to 26-4 in tiebreakers this season when he smacked a forehand approach shot and Murray put a backhand into the net.

A year ago, Roddick lost in the second round at Wimbledon, prompting some serious soul-searching. He was traveling in the States the day of the 2008 Wimbledon final, which Federer lost to nemesis Rafael Nadal 9-7 in the fifth set in fading light. Roddick wound up staying at the airport to watch the end of the match on TV.

Now it will be Roddick trying to beat Federer with a Wimbledon championship at stake.