Serena Williams suffered a nasty knockdown, but she came back in dramatic fashion to finally score a knockout against Maria Sharapova in the Australian Open semifinals.

Fending off three match points, Williams kept her cool and finally found the range on her forehand to win 2-6, 7-5, 8-6. Two times she nailed forehand winners to the opposite court to stay alive. She saved three break points at six games all in the third set and then ended the match by breaking Sharapova on a crosscourt backhand winner.

Trying to stave off a break point at 4 games all in the second set, Williams hit a timid backhand volley. Sharapova scrambled and smashed a crosscourt backhand past Williams, who did a split before falling in a heap on the court.

But the normally unflappable Sharapova opened the door for Williams in the very next game, double-faulting on break point with a 5-4 lead.

The match between the once unbeatable Williams and the 17-year-old Russian phenom was hardly one for the history books. Both players were prone to ghastly errors more often than pretty winners. Williams played flat-footed for the entire first set, hitting off her back foot and letting Sharapova dictate the points. The Russian was ahead 4-1 in no time and ready to run off with her third consecutive victory over Williams, a streak that began at the 2004 Wimbledon final.

The best tennis came in the second set. Serving at three games all, Sharapova saved one break point at 15-40 when Williams caught an unlucky let cord, handing Sharapova an easy forehand winner. Then at 30-40, the Russian benefited from a generous call on a forehand that replays showed to be wide.

“That was so out!” Serena yelled, but the chair umpire said it was too close to warrant an overrule. Sharapova saved another break point before holding on.

Third set was the ugliest of them of all. After a lengthy bathroom break, the women returned and looked like they had forgotten that a match was on, not a practice session. One error was more hapless than the other. Sharapova even forgot to grunt.

Williams started off worse, missing a backhand down the line to give Sharapova an early break. Sharapova returned the favor a game later, and the two traded holds until Sharapova broke through again to take a 5-3 lead. As she did several times in the match, Williams was unable to put an easy shot away, this time giving Sharapova a chance to hit a perfect lob for a winner.

But Sharapova could not serve out the match. Earlier this week, Williams bristled when asked if she and her sister were on the decline. “I don’t appreciate that language, to be honest with you,” she said. Early Thursday in Australia, she certainly was not the Serena Williams of old, but she was good enough.