Valera was diagnosed with a patellar tendon rupture in his right knee Monday, Mandy Bell of MLB.com reports.
Valera was placed on Triple-A Columbus' 7-day injured list Friday due to what was initially listed as a right knee strain, but further tests revealed a more serious injury. He will undergo surgery Wednesday, and the expected recovery window is 6-to-9 months. The 23-year-old will finish his season in Triple-A with a slash line of .248/.337/.452 with six stolen bases, 17 home runs and 50 RBI across 374 plate appearances.