The No.13-seeded Kirilenko came out firing, racing through the first set and eventually building a 61 10 lead with points for 61 20. Radwanska started finding her range from there and fought back to win the second set and build that 3-1 lead in the third; but the momentum swung again as Kirilenko fought back, winning the next four games to lead 5-3 - she stumbled slightly but ended up closing it out.
Kirilenko had lost five straight times to Radwanska but had pushed the last two to 7-5 in the third.
"Every time we play it's so difficult; every time it seems like déjà vu, the score is the same, everything is the same," Kirilenko said. "Just today I was a little bit more lucky. I lost to her the last four or five times I think, and it was kind of a similar match to previous ones, but this time it worked out for me."
Though she can rifle winners at will, Radwanska is known as a player who mixes things up, hitting a variety of paces, angles and spins. Kirilenko was asked how difficult it is to get a rhythm with her.
"Well actually I'm also the kind of player who's playing a different ball," she said. "Of course to beat Agnieszka you need to be more aggressive at times. You have to really focus on every point too."
Next up for Kirilenko will be No.6 seed Petra Kvitova, who downed No.19-seeded countrywoman Klara Zakopalova, 62 63. There was one tense period of the match later on as Kvitova lost three straight games from 62 50 up, but she blasted an ace to kick off the 62 53 game and ended up holding at love.
It was Kvitova's eighth win in a row, and actually her 18th win in her last 20 matches in North America - if you add in her very strong summer hardcourt season from last year, during which she won Montréal, made the semifinals of Cincinnati, won New Haven and made the fourth round of the US Open.
"I think last year was the first time I played quite well in the US Open Series - before I didn't like the weather in America, but it's much drier here at Indian Wells so it's better for me," Kvitova said. "I remember even Montréal, Cincinnati, New Haven and US Open weren't so good conditions for me, but I was quite lucky in that I played at night mostly. And this is the first year I'm playing well here."
Kvitova and Kirilenko are tied in their head-to-head series, 3-3. Their last two meetings couldn't have been closer, though - Kirilenko won a very tight two-setter in the quarterfinals of the Olympics last summer, and just a few weeks later, Kvitova won a very tight two-setter in the New Haven final.
"Petra's a really good player. She just won a big tournament in Dubai," Kirilenko said. "That means she's in good shape right now. The last couple of matches we've played have been tough, long matches, so I think this one will be another big one. It will be completely opposite to today's match.
"I just need to be there. I need to be thinking fast. It's not going to be slow, long rallies, you have to be quick against her. Everything's going to be quick. I just need to concentrate, and that's it."