Serena Williams, once again, prevails over herself

Serena cruises in straight sets at Indian Wells (5:37)

Top-seeded Serena Williams advances in straight sets with a 6-2, 6-2 victory over Kateryna Bondarenko. Agnieszka Radwanska, Petra Kvitova and Simona Halep also advance at Indian Wells. (5:37)

The Indian Wells semifinal between top-ranked Serena Williams and new WTA No. 2 seed Agnieszka Radwanska was an interesting match, but not nearly as compelling as the battle between Williams and herself.

Williams overcame another slow start to handle Radwanska, albeit with some tricky interludes, 6-4, 7-6 (1). Once again, it seemed Williams was trying to demonstrate the truth of all those bulletin board clich├ęs about winning the battle with yourself.

It's been this way for quite some time for the 21-time Grand Slam champion, going back to last year -- maybe even earlier. It's hard to say why; perhaps even Williams doesn't know. But every great champion knows that it gets hard to muster the passion for battle day-after-day in the late stages of a career. Williams won eight Grand Slam titles after she turned 30. It's an amazing record, but surely one that's taken a heavy mental and emotional toll on a woman who has played professionally since the age of 14.

Clearly, Williams is still a fighting champion; it's a measure of her uber-greatness that she is so conspicuously struggling within -- and still winning.

Match-to-match, the question that materializes time and again out of that fog of unforced errors and poor footwork is: "Will Serena come out of it, find her game, win again?"

It often appears that she's running on fumes, and perhaps in some ways that's true. But she is a woman of remarkable physical and emotional strength and will, and if that isn't enough, there's always that ability to exercise the equivalent of the nuclear option: that magnificent serve.

Williams doesn't hesitate to deploy that weapon; in fact, the match with Radwanska demonstrated once again that it might be the single outstanding reason she can waltz with danger and still end up winning. That serve sometimes tells the entire story, but on occasions like this one it tells just half.

Williams didn't have a great night at the service notch (she hit six double faults and five aces, and put just 55 percent of her first serves in play). But she still won 67 percent of her first-serve points.

More important, Williams trusts her serve, and it rewards her with critical points. It's a dispiriting experience for an opponent, especially one like Radwanska. Despite all Radwanska's gifts, she's doesn't have a serve to match Williams'. And that was the other half of the story in this one.

Williams, whose lethal return is overshadowed by her serve, feasted on Radwanska's second serves (she won 61 percent of those points), and also won a healthy 42 percent of Radwanska's first-serve points. It was a tough one-two punch to absorb for the woman who's amassed the most WTA wins since the last US Open (Radwanska was 34-6 before meeting Williams).

Radwanska broke Williams in the first game and quickly built a 3-1 lead. Once again, Williams looked like a reluctant warrior. It was so hard to read anything into her facial expressions that she might have been pondering the hole in the ozone layer rather than the holes in Radwanska's game.

Williams didn't really snap out of it until she broke back for 4-all, and then she was off on what became a seven-game run that left her leading 3-0 in the second set. The new, improved Radwanska pushed back and refused to give up, goading Williams into playing her best.

The final 10 games were of high quality, until Williams doused Radwanska's lights swiftly in the tiebreaker. Williams served and lost the first point on a volley error, but then she ripped back two consecutive first-serve return winners and won the next two points with her big serve to build a 4-1 lead that finally broke Radwanska's resistance.

"She was really determined; she never gave up," Williams said of Radwanska in her on-court interview. And of her own slow start she said, "Well, towards the end of the second set I figured I could really give a thousand percent right now."

She gave it, and all of it was needed to get her into Sunday's final.