There's little to choose between Rafael Nadal and Roger Federer heading into this week's French Open.
Four-time champion Nadal is the online betting favourite after making a winning return this season from a career-threatening knee injury.
Meanwhile, world number one Federer is the defending champion after taking full advantage of Nadal's injury problems to claim his maiden title at Roland Garros 12 months ago.
But should the unthinkable happen and Nadal and Federer both fall, which dark horse is most likely to win this year's second Grand Slam tournament.
The already short list of candidates has been cut dramatically in recent days following a spate of withdrawals.
David Nalbandian, Martin del Potro, Nikolay Davydenko, Gilles Simon, Tommy Haas and Igor Andreev have all pulled out through injury which leaves only a few men standing.
The most obvious dark horse is Novak Djokovic as the Serb is currently ranked third in the world behind Nadal and Federer.
However, the best the 22-year-old has managed in the French Open is two semi-finals, while last year's fourth-round defeat in straight sets to Philipp Kohlschreiber highlighted his uneasiness on the Paris clay.
World number four Andy Murray's record at Roland Garros is even worse than Djokovic and the British number one might be best avoided this week.
His form heading into the tournament is erratic at best and his Paris highlight is a quarter-final defeat to Fernando Gonzalez 12 months ago.
Perhaps better dark-horse bets would be Spanish duo Fernando Verdasco and David Ferrer, despite their own patchy record in the year's second Grand Slam.
Verdasco reached back-to-back finals in Monte Carlo and Barcelona earlier in the clay-court season and emerged triumphant in the latter after edging out Robin Soderling.
At last week's Italian Open he lost at the semi-final stage to Ferrer and his fellow countryman cannot be discounted.
He was well beaten by Nadal in the final but it is surely only a matter of time before the 28-year-old from Valencia improves on a disappointing Grand Slam record.
Ranked below the Spanish duo are the likes of Soderling, Marin Cilic, Gael Monfils and Jo-Wilfried Tsonga, but it's hard to see the winner coming from this group of current also-rans.
Not since Gaston Gaudio in 2004 has a relative long shot won this blue-ribbon event and it's unlikely to happen this year.