Roger Federer had the second best year in men's tennis last year. No one expects the 34-year-old to continue at this level forever, but Federer still clutched the World No. 2 ranking headed into Rome this week. Even with Kei Nishikori and Stan Wawrinka playing well, the Big Four -- with the re-emergence of a fit Rafa Nadal -- has looked as impermeable as ever barreling toward Roland Garros and the year's second Grand Slam at the end of the month.
But Federer got tripped up in Rome, losing to 15th-ranked 22-year-old Austrian Dominic Thiem and failing to achieve the quarterfinals. Thiem took advantage of a Federer back injury that slowed the Swiss, needing just two (tough) sets to win 7-6(2), 6-4. Federer recently withdrew from the Madrid Open with the same back injury. His grasp on the No. 2 ranking is tenuous. The 2016 French Open begins May 22.
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