At the 2010 US Open, Isner was 18th seed and defeated Frederico Gil in the first round. After the match he revealed that although the initial diagnosis was a right ankle ligament tear, a second opinion revealed that the damage was a strain and not a tear, and he declared his ankle 90% healed. He then advanced to the third round, before losing to 12th seed and 2006 US Open semifinalist Mikhail Youzhny. The loss dropped Isner out of the top 20 and from the no. 2 to the no. 4 ranked American player. Due to his ankle injury, he chose not to compete in doubles.