Andy Roddick meets Roger Federer. Again. Will it be any different this time?

Tonight, in the U.S. Open quarterfinals, Roddick will look over the net at the man who has denied him perhaps three or four major titles. The man who has beaten him 13 out of 14 matches and nine in a row. The man who seemed to be within reach, or at least distant reach, at last year’s U.S. Open, when Roddick won a set in the final, and then seemed infinitely far away at the Australian Open this year, when the world no. 1 rattled off 11 consecutive games and 24 of 27 points in a humbling 6–4, 6–0, 6–2 decision.

That was seven months ago, before Roddick crashed out of Wimbledon, missing another chance at Federer, and followed it up with an uneven summer. In Australia, he felt great and played several strong matches on his way to the semifinals. Everyone expected him to build on his performance at the year-end Masters Cup, where he held three match points against Federer before victory escaped him again. Instead of building, Roddick went bust.

At the Open this year, unlike in Australia, there’s no sense that Roddick might actually put up a fight. If Federer’s dominance isn’t enough of an explanation, add the fact that Roddick has played little tennis this tournament, through no fault of his own. Two of his first four opponents retired, one after winning the first set and the other after nearly doing the same. He had a surprisingly difficult time, at least early on, against Justin Gimelstob in the first round, and a surprisingly easy time against veteran Thomas Johansson, losing a mere five games in three sets. After Tomas Berdych walked off the court on Monday, Roddick jogged over to the practice courts for another 45 minutes. Strange for a top player to arrive at a quarterfinal match against the best player in the world and feel uncertain of his form, but that might be the case tonight. At least he’ll be fresh.

He won’t be uncertain of his plan of attack. A lot must go right for Roddick to beat Federer — no matter how well Roddick plays, he’ll need Federer to perform at less than his best (if, for example, Federer ticks off 35 consecutive points on his serve, as he did against Feliciano Lopez, Roddick won’t beat him with a 30 caliber rifle). But if Federer struggles a bit, and Roddick serves incredibly well, swings away at Federer’s second serve, and attacks the net when he can, then maybe — maybe — the match will turn in his favor. Roddick can learn something from John Isner and Lopez, the two men who stole a set from Federer in this tournament. (An aside: Both Isner and Lopez won the first set, which is essential against Federer. He’s 49–6 this season, but 4–6 after losing the first set. In his run of three straight U.S. Open titles, from 2004 to 2006, he didn’t lose the first set in a single match.)

Isner, the 22-year-old fresh out of the University of Georgia, already has one of the biggest serves on the tour, and Lopez, a Spanish lefty who honed his game on hard courts, not clay, isn’t far behind. But what’s most interesting about their performances is that they essentially went for broke on their second serves. Isner often serves 120 mph on his second attempt. Lopez doesn’t, but he did a few times Tuesday evening. In the first set, he won 94% of his first serve points and 55% of his second serve points. He well understood what Roddick, to some extent, has been unwilling to admit. If Federer puts the ball in play and starts a rally, he’s likely going to win the point. Best, then, to keep the ball out of play at all costs.

When people talk about why Roddick doesn’t beat Federer, his serve isn’t cited as a cause for concern. In reality, it might be the chief problem. Roddick always serves well, but he needs to serve better than that — perhaps better than he ever has — to win, and he won’t accomplish that without taking more chances on his serve, as Lopez did on Tuesday evening (the Spaniard closed out the first set with a booming second serve that Federer fired into the net). Roddick won’t ever outhit Federer in baseline rallies or outmaneuver him at the net. He can’t outrun him. But he could, conceivably, serve him off the court.

The stats from the last 10 matches Roddick and Federer have played — nine wins for Federer and one win for Roddick, in Montreal in 2003 — suggest that Roddick hasn’t gambled enough on his serve. Roddick, throughout his career, has generally won 80% of his first serve points and about 56% of his second serve points. Only one time in those 10 matches against Federer did Roddick win more than 47% of his second serve points, and that was in the match he won (63%). At the Masters Cup last year, when Roddick held three match points and won 80% of his first serve points, the best first-serve performance in those 10 matches, Roddick won 47% of his second serve points. At last year’s U.S. Open, he won 38%. At this year’s Australian Open, 29%.

The best way for Roddick to win more second serve points, at least against Federer, is to follow the Lopez method: Hit more first serves. Yet in his last three matches against Federer, Roddick has double faulted a total of four times. This may sound strange, but that’s not enough. If Roddick serves well and takes more chances, he’ll lose more points on double faults, but odds are he’ll win enough free points, or set up enough easy forehands or volleys, to make up for those errors.

Against Federer, spinning in a solid second serve, even one that kicks as high as Roddick’s, simply delays the inevitable. It’s a double fault by a different name. If you are rooting for Roddick, pray that he lets the serves fly, faults be damned.

Mr. Perrotta is a senior editor at Tennis magazine. He can be reached at tperrotta@nysun.com.