Mattek-Sands had taken out No.6 seed Li Na en route to the fourth round and came out swinging again, storming out to a 4-1 lead in the first set, but the No.12-seeded Kirilenko snatched the momentum from right underneath her, winning nine of the next 11 games to build a 75 31 lead. The two players went into a holding pattern from there until Kirilenko finished the American off, 75 64.
"I actually felt like I didn't play well today - I was struggling with my shots a little bit, with my serve, everything," Kirilenko said after the match. "I went on court and suddenly I was down 1-4. I felt like nothing was working. But I decided it was okay. I'm an experienced player, so maybe I just needed to take some time and relax. And after that I was actually sure I was going to win the match today."
Kirilenko is now through to the quarterfinals here for the first time. It's her third Grand Slam quarterfinal, having already done it at the Australian Open in 2010 (falling to Zheng Jie) and at Wimbledon last year (falling to Agnieszka Radwanska). She has never gone beyond the quarterfinals of a major.
"I had some opportunities to make the quarterfinals here in previous years but it didn't happen - so now I turn 26 and I've finally done it," Kirilenko said. "I think the age in tennis is going a little bit further. Everybody's starting to show their best results after 30 now. I don't know why, but it's good for them."
Mattek-Sands had equalled her best Grand Slam, having reached the 16s of Wimbledon in 2008.
"The match was good - Maria played great, she's tough," Mattek-Sands said. "I started out strong and then made some mistakes, but I feel like I fought hard and did my best to try and come back. I have a lot to build on from this, so I'm happy with my tournament. I'm happy with my effort. You know, mistakes are mistakes, but I'll have a lot of stuff to work on during practice going forward now."
Speaking of going forward, where does the American go next? "The scheduling is pretty important now because I've played a lot of matches for this first part of the year, and obviously I'll get into some more tournaments now that my ranking is going to be a little bit better. That kind of changes things as well. But for the most part I know in advance what tournaments I want to play. Obviously grass, Wimbledon and the US Open Series. I love all the tournaments there. And then after that, I haven't played Asia yet - I've been hurt every year and never had a chance to go out there and play. Right now I'm signed up for the WTA tournament in Germany next week, which is on clay, and then we'll see after that.
"But I'm still in doubles here - we'll play tomorrow."
Next up for Kirilenko is No.3 seed Victoria Azarenka, who beat Francesca Schiavone earlier in the day. Azarenka leads Kirilenko in their head-to-head, 3-2, and has won the pair's last three meetings.
"I have to be ready for anything - physically I have to be good, I have to serve good, I mean, in everything I have to be good to beat Vika," Kirilenko said. "That's the only chance I have to beat her."