Rafael Nadal and Roger Federer have combined to win 21 of the last 23 major championships, but Novak Djokovic, Andy Murray and Robin Soderling are primed to challenge that hegemony in 2011.

The biggest X factor is Juan Martin del Potro, the big-serving Argentine who outlasted Federer in the 2009 U.S. Open final. Then 20, Del Potro rapidly climbed to No. 4 in the rankings, but subsequently missed 10 months with a wrist injury. Whether he can regain form is one of the year's most significant plotlines.

Andy Roddick is the only player besides Federer to have finished in the year-end top 10 for the past nine seasons, but his days at the summit of American tennis may be numbered with John Isner and Sam Querrey waiting in the wings.

Here's how SI.com's tennis experts see the upcoming men's season playing out.

EXPERTS: Fantasy Tennis: Building the Ideal Player for 2011

JENKINS: Ten things I'd like to see in 2011

GALLERY: Tennis Players to Watch in 2011

GALLERY: 20 Must-Follow Tennis People on Twitter

WERTHEIM: Ten fearless prognostications

REACT: Weigh in with your predictions for 2011

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