17-time Grand Slam title winner Roger Federer joins Rafael Nadal, Novak Djokovic on Twitter24 May 2013, 7:27 AM PDT
Defending Sprint Cup champion Keselowski struggling to follow up on title-winning season24 May 2013, 7:17 AM PDT
2-time defending champion Luke Donald, Ian Poulter miss cut at PGA Championship in England24 May 2013, 6:38 AM PDT