Rafael Nadal: Knee pain meant I had to retire in semifinal Unknown 00:11 After retiring through injury at the U.S. Open, Rafael Nadal said he was simply in "too much pain" to continue his semifinal. Share this Share on FacebookTweet on TwitterPlus on Google+ Related PostsLynx's Fowles breaks WNBA record in 75-62 win over MercuryMichigan adds to Juwan Howard's basketball staffTigers purchase Triple-A contract of pitcher Trevor RosenthalThree Cuts: Red-hot Josh Donaldson providing one of biggest free-agent returns on investmentReid scores 20, Wolves advance to summer league title gameVIDEO: The Successful Batter by Willie Horton (Part 1 of 4)