Any doubts who the French favorites are?

Rafael Nadal and Justine Henin won important clay-court titles Sunday, and you couldn't blame the two if they performed a duet of that old sing-along tune, "Happy Days are Here Again." Nadal and Henin have a grand total of eight French Open titles between them (four apiece), but neither was able to bag the main prize at Roland Garros last year.

Nadal, upset by Robin Soderling in the fourth round at Roland Garros last year, had won four consecutive titles in Paris going into 2009, and any doubts about the severity of his knee injuries was laid to rest when Nadal was unable to defend his Wimbledon title just a few weeks after his loss to Soderling. Henin was basically MIA in '09, having gotten it into her head to "retire" from tennis a little more than a year earlier. Unlike her decision to get back in the hunt, it was a poorly thought out and needlessly dramatic gesture.

But Nadal is healthy now, and Henin is thinking that maybe being an elite pro tennis player isn't such a bad gig after all. With their wins in Rome (Nadal) and Stuttgart (Henin), they've established themselves as the odds-on favorite to continue their competition for who can end up with the most career titles at Roland Garros. Nine, anyone?

Now that Kim Clijsters is out with a foot injury and likely to miss Roland Garros, you have to wonder if anyone can stop Henin. If you'd asked that question two weeks ago, you might have gotten a host of affirmative responses. But we've forgotten that Henin is quite a different player on clay than on hard (the only surface she's competed on since returning to the tour in January). If there's a technical reason for why Henin looks so much stronger on clay, it's that she has that extra smidgen of time to draw a bead and dictate how a point will play out. Clay gives her that extra inch that enables her to take a mile.

Henin has another advantage: Very few of the players who can hurt her are deadly on clay. And some of those who might be able to do it have issues -- serious issues. We'll see over the next few weeks if any of the usual suspects -- Serena Williams, Jelena Jankovic, Svetlana Kuznetsova, Dinara Safina, Victoria Azarenka, Caroline Wozniacki -- can do anything to convince us that Roland Garros isn't Henin's to lose.

Nadal is in an even stronger position than Henin. He's 10-0 on clay this spring, and his prime challenger (if you go by the W-L record on clay this year) is ... Fernando Verdasco. You have to go back to the heyday of Bjorn Borg to find so overwhelming a favorite for Roland Garros.

You know, they say that clay is the great equalizer, and the surface most likely to weed out impostors and also-rans. The premium on clay is consistency, although the big winners are those whose games have a value-added component -- call it "consistency plus." In Nadal's case, the plus is his remarkable athleticism and stamina. For Henin, the added value is her absolute command of the stroking repertoire; has any woman so successfully melded consistency on clay with inventiveness?

With three weeks to go until the French Open, Nadal and Henin have positioned themselves as the favorites. The most interesting rivalry might be between them, to see who gets to five or seven or nine or 11 French Open titles first.

I say it will be Henin, but only because the women play the final on Saturday, one day before the men.