Andy Roddick played one of his better matches against Roger Federer Wednesday night in the quarterfinals of the Sony Ericsson Open.

All the No. 5 American received for his considerable improvements, however, was yet another loss to his Swiss nemesis. Federer, aided by a fortuitous net-cord winner on the penultimate point of the match, closed out Roddick in three tight and tension-packed sets, 6-3, 4-6, 6-4. The two-hour triumph sends the second seed into Friday’s semifinals against No. 3 Novak Djokovic.

There’s a very simple reason why Roddick held a post-match press conference that lasted all of 90 seconds: He played extremely well for most of this match, yet had to watch one of tennis’s great champions receive help from the tape at crucial stages of this confrontation at the Crandon Park Tennis Center.

One year ago, Roddick beat Federer at this same stage of the Sony Ericsson Open, digging out of a love-30 hole at 3-all in the third set to swing momentum in his favor. Once Roddick held for 4-3, he won eight of the final 10 points to win his second career match against Federer. As the two men returned to Miami for a South Florida sequel, a surprising case of role reversal emerged before a lively and energetic crowd.

This time, it was Federer’s turn to get out of jail at 3-all in the third set. After three overcooked forehands created a 15-40 deficit, Federer painted the sideline with an inside-outside forehand to get to 30-40. Then came one of two points that would tell “the tale of the tape,” the top of the net that had a lot to do with the outcome of this riveting affair.

On the 3-all, 30-40 point that saved his hide, Federer hit a forehand that ticked off the tape and bounced high into the air. As is the case with the U.S. Open (but unlike Wimbledon), the nets at this tournament are tightly strung, which creates severe bounces with long arcs and high trajectories. Hitting the tape on a full-swing groundstroke often causes the ball to land beyond the baseline, but in this case, Federer’s shot landed just inside he baseline. Roddick made a decent reply from the backcourt, but Federer was there to hit a delicate crosscourt drop volley from his forehand wing. Once at deuce, a clearly relieved Federer comfortably won the next two points to hold for 4-3. After withstanding Roddick’s best tennis for the previous one and a half sets, Federer gained an extra degree of comfort once he saved those two break points. Federer pushed Roddick to three deuces in the American’s 3-4 service game, and although Roddick held, a different story emerged just moments later. Once again, the tape would tell the tale.

Serving to stay in the match at 4-5, Roddick gained a 40-15 lead and figured to push the match one step closer to a decisive tiebreak. But in a match where 40-love leads weren’t automatic (Federer suffered his one break of serve in the second set after leading by that score; the abrupt turnaround represented the difference in the set), Roddick couldn’t find the huge first serves and cheap points he needs. Federer constructed two points to achieve deuce, and Roddick suddenly put himself in a precarious position.

On the deuce point, Federer hit a crosscourt backhand pass that Roddick anticipated at the net. However, Federer’s shot hit the tape and took one of those typically high and long bounces. Roddick had no chance to get his racket on the ball, which landed comfortably in the corner of the court for a winner. Because of his lucky break, Federer had match point on the next point, and this time, the Swiss superstar nailed a backhand pass that was nasty, low, and filled with bite. Roddick barely touched the shot, and in a stunningly abrupt sequence of events, Federer moved to 17-2 in his head-to-head series with Roddick.

Federer did get enormously lucky on a night when the Swiss missed a lot–40 times, to be exact. Nevertheless, Roddick learned that despite his bad fortune, the best way to prevent another case of heartbreak is to finish service games when one has the chance. Roddick profited in the second set when Federer lost a 40-love lead; in the end, it was Roddick’s inability to preserve a 40-15 advantage that allowed the net cord to influence the outcome of a quality quarterfinal.

Andy Roddick is clearly improving at this advanced stage of his career. With continued determination and more high-level tennis, the American will knock the door down again when he fights with Federer. More to the point, he won’t put himself in a position where a few net cords can ruin his plans.