Stress was spiking as Argentine qualifier Federico Delbonis spun a forehand smack off the baseline in the sixth game of the second set prompting Roger Federer to kick the red clay creating a rising cloud of frustration.

Federer debuted his new Wilson racquet in Hamburg this week, but Delbonis found the sweet spot when it mattered most, giving the top-seeded Swiss the boot, 7-6 (7), 7-6 (4), to score the biggest win of his career and reach his first ATP final.

Empowered by saving two match points in subduing 14th-seeded Fernando Verdasco 6-7 (5), 7-6 (8), 6-4 in three hours and 15 minutes yesterday, Delbonis did not look fazed facing Federer before a packed center court stadium today.

Repeatedly ripping his heavy lefty topspin forehand into Federer's backhand wing, Delbonis stretched the four-time Hamburg champion. When he wasn't doing damage with his heavy forehand, the 114th-ranked Delbonis showed some fine feel on the drop shot in denying Federer much say in his service games. Hooking his lefty serve into Federer's one-handed backhand on the ad side, Delbonis created space and mid-court balls in winning 82 percent of his first-serve points and 68 percent of his second serve points, while facing just two break points.

Federer rifled a backhand pass to earn his lone break for a 2-1 lead in the opener before Delbonis rapped a forehand winner for break point. When Federer netted a backhand, the 22-year-old Argentine was back on serve at 2-all. From 4-all, the pair traded three consecutive love holds before Delbonis earned two set points on Federer's serve at 5-6. The Swiss snapped off a pair of stinging serves down the middle to erase both set points, eventually serving his way into the tie breaker. Federer opened a 4-2 lead in the breaker and earned set point at 6-5, but Delbonis saved it with a service winner out wide. Federer fought off a third set point with a serve down the middle, but was passed easily on a serve-and-volley attempt. On his fourth set point, Delbonis dragged Federer wide, rapped a forehand into the corner than charged forward to block a forehand volley winner and collect the first set in 49 minutes.

Ultimately, the 17-time Grand Slam champion couldn't exert enough pressure in the 22-year-old lefty's service games. After surrendering serve, Delbonis held at love in four of his next six service games. Federer's backhand chip return is his preferred play, but he wasn't gaining much traction from it and might have been wiser to run around the backhand return and hit his forehand at times or loft some higher, heavier backhands deep down the middle to deny Delbonis angles or try hitting a few backhand returns down the line on the ad side, though the problem with that tactic is if he doesn't execute with precision, then he exposes the entire court to his opponent.

Federer fought off three break points in the first game of the second set, firing a forehand winner down the line to dig out a demanding hold. Delbonis reached deuce in three of Federer's first four service games of the second set, blasting a backhand return winner crosscourt off a serve-and-volley to gain a break point at 3-all, but Federer slammed an ace down the middle to save it. In the ensuing game, Delbonis saved the only break point he faced in the second set, scrambling to stay alive then blocking a reflex forehand volley into the open court, eventually holding for 4-all.

A mis-hit forehand and shanked backhand from Federer gave his opponent double match point and when the Swiss slapped a forehand into the middle of the net, Delbonis covered his face with his hand, completing the one hour, 53-minute win. Delbonis, who is expected to rise to a career-high rank of No. 59, will face Fabio Fognini, who swept Nicolas Almagro for his ninth consecutive victory, in the final.