Perez elected to have the surgery now so that he can immediately begin his rehab and try to return at some point during the 2015 season. The recovery time after Tommy John surgery is typically 12 to 18 months.
"The ligament is not 100 percent and I think it's best for me to get this done now," Perez said. "It was not an easy decision, but I want to get the surgery and start on my rehab."
Perez was placed on the 15-day disabled list on Wednesday after an exam revealed a partially torn ulnar collateral ligament in his left elbow.
The 23-year-old was 4-3 with a 4.38 ERA, but started the season 4-0 in his first five starts with a 1.42 ERA in 38 innings, picking up where he left off in 2013. Then, Perez was 10-6 with a 3.62 ERA in 20 starts, joining the rotation for good in late June. Perez earned a long-term contract in the offseason, signing a four-year, $12.5 million deal with three club options.
He said he felt some pain in the elbow only in his most recent start, when his velocity dipped and he gave up six runs on nine hits in 3⅔ innings against Boston on May 10.