MELBOURNE, Australia(AP) Serena Williams watched Svetlana Kuznetsova stroll to the service line, getting ready to serve for the match.

Failure to break would prevent Williams, a three-time Australian Open singles champion, from having any chance of picking up her coveted 10th Grand Slam title.

So was Williams trying to figure out what Kuznetsova might do with her first serve? Maybe thinking about whether to stay back and slug it out or try to pressure the Russian by rushing the net?

Nope.

She was looking for motivation, and she found it by imagining what it would be like to make the long flight across the Pacific to the United States as a quarterfinal loser.

In the most cramped seat possible, with a lot of time to fume over a missed opportunity.

I was thinking, 'OK, if you lose, you're going to fly coach all the way back to Florida, how uncomfortable that would be?' Williams said, laughing. ``That motivated me to do a little better.

``I wouldn't allow myself to have the emergency row either. I would be so mad, I would have to sit like (in) the last row, the tightest row. That way I wouldn't do it again.''

No worries. Williams broke Kuznetsova's service, evened the set at 5-5, broke a game later and went on to a 5-7, 7-5, 6-1 win.

She can keep her business- or first-class ticket for at least another day - at least until she plays Elena Dementieva in Thursday's semifinal.

Dementieva advanced to the semis with a 6-2, 6-2 win over Carla Suarez Navarro in the other quarterfinal. The unseeded Suarez Navarro beat Serena's sister Venus in the second round.

Dinara Safina will play fellow Russian Vera Zvonareva in the other semifinal Thursday.

Temperatures in excess of 104 degrees forced the tournament to invoke its Extreme Heat Policy. That suspended matches on outdoor courts, shifted some of them to a second indoor arena and, eventually, closed the roof at Rod Laver Arena after the first set of the Williams-Kuznetsova match.

Dementieva played Suarez Navarro in the first match at the main show court with the roof open and the temperatures just about as hot as when Williams played. Dementieva, the Beijing Olympic gold medal winner, wondered why there seemed to be a different set of ground rules for the two matches.

It looks like nobody really knows how it works here,'' Dementieva said of the heat policy.I think when it's 40 (104 degrees) and over you have to close the roof. But saying that in our match, it was like 39 and a half, well, I don't know. When you're on the court it feels like 45 ...''

Kuznetsova felt the same way, particularly after she won the first set with the roof open, and lost the next two with it closed.

It's two different games, one you play inside; one you play outside,'' Kuznetsova said.She has a big serve, and she was using it very well when the roof was closed. It was in her favor very much.''