The second-highest-ranked American John Isner will return to River Oaks for the U.S. Men's Clay Court Championship on April 5-11. Isner, who is ranked No. 28 on the ATP World Tour, is the fourth Top 30 player to commit to the event, joining No. 11 Fernando Gonzalez, No. 17 Tommy Haas and No. 29 Sam Querrey.