So here's what will happen in the world of tennis in 2017 in a season that will feature a comeback for veteran stars Roger Federer, Maria Sharapova, Serena Williams and Rafael Nadal. Federer has some work to do to return to the top five, given his inactivity since deciding to end his season in July. But, if reports are to be believed, the Swiss legend is in great shape as he trains in Dubai. Motivation remains sky high for Federer -- the 35-year-old plans on playing a couple more seasons -- and even when injured he came close to reaching the final at Wimbledon.