It ended as only a hacker can dream: With a crisp, down-the-line backhand winner on match point against a formidable opponent, under the lights on center court at one of the most prestigious tournaments of all.

But how Flavia Pennetta arrived at that wonderful moment, one which secured her 7-6 (5), 6-3 semifinal win over top seed Li Na, wasn’t as ethereal. In fact it could largely be described as what that very hacker does in reality—missing more than she makes.

Pennetta was half pro, half cat on Friday night: She had four-a-half-lives. The Italian led Li by a break of serve four times in the first set, and not once was she able to consolidate with a hold. After failing to serve out the set at 5-4 and 6-5, it seemed unlikely that Pennetta could hold it together for the tiebreaker.

Fortunately for Pennetta and unfortunately for fans of clean tennis, Li was even shakier. Her forehand was a mess all day, taking the ball to far away places and succumbing during rallies both long and short. Her serve was occasionally unusable. She double-faulted four times at 4-4, including on break point, to give an equally erratic Pennetta hope in a set filed with despair.

Li’s 30th unforced error gave Pennetta a 3-1 lead in the tiebreaker, but two sharp backhands from the Australian Open champion leveled the score. Pennetta recovered the mini-break lead at 6-4 with a great defensive reply to a strong cross-court backhand by Li, who eventually put a weak backhand into net. But while Li saved the first set point with confident play, the second point ended as only this set could, on an error: Her eighth double-fault of the match.

Li would only hit one more double fault this evening, but her serve remained a liability that Pennetta continued to expose in the second set. Li won less than half of her first-serve points and was broken six times overall; she never once appeared to be in a comfortable state on court. Pennetta, however, gradually found her form. While she couldn’t match her opponent in the power department, Pennetta used Li’s pace against her, changing the complexion of exchanges in an instant, without warning.

When Li held serve for a 2-0 second-set lead—the first hold in 10 games—it appeared an indication that the match might turn. But it would only turn back toward Pennetta, who would hold serve the rest of the way while exuding intense focus with the upset near her grasp. Li’s mistakes and frustration, meanwhile, were mounting. She finished the match with 52 unforced errors and an astounding 111 over her last two matches.

Pennetta finished in style, but not without some struggle. She never had to save a break point in the final game, but she overcame a 0-30 deficit and shook off a match point that came and went. After winning on her second chance, she’s in her first WTA Premier-level final, and will look to realize her dreams Sunday against Agnieszka Radwanska.