Beat Roger Federer once, and it’s usually considered a fluke. Beat him twice in less than three weeks? That’s called a fantasy.

Guillermo Canas is living it. The 29-year-old Argentine, who returned earlier this year from a drug suspension, continues to mystify the world no. 1 with his consistent strokes and boundless energy. Yesterday, Canas knocked Federer out of the Sony Ericsson Open in Miami, 7–6(2), 2–6, 7–6(5).

At the Pacific Life Open in Indian Wells, Calif., two weeks ago, Canas dumped Federer in straight sets. Yesterday’s victory was more impressive in that Federer doubtless wanted to exact revenge — and should have. He led 2–0 in the second set and had four break chances for 3–0 before Canas held and eventually broke back. In the tie breaker, Federer set up a volley by hitting a second serve on his first serve; Canas didn’t expect the ball to land short and kick high, and he could only lob it over the net. Federer stepped into position, but lost his composure. Do I hit an overhead? A volley? Let it bounce? He went for a swinging forehand volley and fired it into the net. On match point, Canas served up the middle, and Federer whiffed. Yes, whiffed.

Canas deserves the credit here, and a lot can be learned (by everyone else on tour save Rafael Nadal) about how to rattle Federer. Canas rarely misses, and he hits with excellent depth and topspin; he has a steady serve; and he hustles, hustles, hustles (sounds like a Spaniard we know). Federer has endless ways to win matches, so about the best an opponent can do is make sure he doesn’t give points away. Canas is as stingy as they come.

Now for the scary part: he’s also a much better player on clay than he is on hard courts. The prospects for the next two months, leading up to the French Open, just got a lot brighter — for fans, if not for Federer. Winning in Paris will be a serious challenge.

In women’s tennis, Maria Sharapova yesterday suffered another drubbing at the hands of Serena Williams, 6–1, 6–1. This one was so easy for Williams that her father and coach, Richard, advised her to play to Sharapova’s strength (Williams says it’s her backhand) so Williams could enjoy a few more rallies before today’s quarterfinal. Sharapova wouldn’t accept her charity, and offered up more of her own in the form of eight double faults.

As defeats go, this one was more embarrassing for Sharapova than her 6–1, 6–2 loss in Australia. Little could stop Serena in Melbourne, but to win only two games in the rematch is weak, especially considering Williams hadn’t played a match between Melbourne and Miami. A few notes of interest to Sharapova’s future opponents: she’s lost confidence on her serve, which in 2005 (and for most of last year) was one of the best on the tour, and hasn’t the faintest idea how to return a slice serve. Williams consistently earned winners off wide serves to the forehand, or short returns off serves that sliced from the center line into Sharapova’s body, handcuffing her. Shahar Peer ought to give Williams a better match if they meet in the semifinals, and a final against Justine Henin would be a treat.

tperrotta@nysun.com