It’s often said that men’s tennis is deeper and more competitive than it has ever been. And it’s true; the sport has never been played at a higher level. But over the last five years, it hasn’t been the excellence of the ATP as a whole that’s been most impressive. It has been the dominance of the top players despite that depth. Since 2006, we’ve seen three players—Roger Federer, Rafael Nadal and Novak Djokovic—put together seasons that rank among the most gloriously accomplished of the Open era.

Now that the third and perhaps finest of those seasons, Djokovic’s remarkable 2011, is complete, it seems like a good time to look back at where it—as well as Federer’s and Nadal’s best years—fits among the greatest single seasons of the Open era. There’s no right answer, and that’s what makes this parlor game so much fun. Here we present our countdown of the 10 best men’s seasons since the Open era began in 1968.

No. 2: Roger Federer, 2006

He’d gone 74-6 in 2004 and 81-4 in 2005. He’d won five Slams in those two seasons, and would win three more in 2007. But the jewel in Roger Federer’s half-decade crown would be 2006. That year, even with a fearsome rival, Rafael Nadal, across the net, Federer put up a mind-boggling series of statistics: He went 92-5, the fourth-highest winning percentage of the Open era. He won three more majors, added a third ATP year-end championship, won 12 of 17 tournaments he entered and reached the final in 16 of them. Just as impressive were his back-to-back titles in Indian Wells and Key Biscayne, a grueling hard-court double. Federer missed the calendar-year Slam by his four-set French Open loss to Nadal, but he avenged that defeat in the Wimbledon final and downed Nadal at the Masters Cup in Shanghai.

Check TENNIS.com each day for the next season on the list.

A version of this story was originally published in the Jan/Feb 2012 issue of TENNIS.