CHICAGO -- Right-hander Edgar Santana will undergo Tommy John surgery, Pirates director of sports medicine Todd Tomczyk announced on Wednesday.
Santana, 26, will miss the entire 2019 season, as pitchers typically return to Major League competition 14 to 16 months after the surgery. Dr. James Andrews, who confirmed the club's diagnosis on Wednesday morning, will perform the reconstructive operation at a date to be determined, Tomczyk said.
Santana exited Friday's game in the middle of the sixth inning after feeling tightness in his forearm and elbow. He also felt "a little bit" of tightness in his forearm in August, Tomczyk said, and the Pirates responded by giving him six days off. Santana returned to make six appearances before his final outing.
"It's really an acute episode," Tomczyk said. "He's had a relatively clean bill of health up until this year."

The news obviously comes as a tough break for Santana, who established himself this season as a legitimate late-inning reliever. He posted a 3.26 ERA and 1.10 WHIP in 66 1/3 innings over 69 appearances in his first full Major League season. Santana began the season as a middle reliever, but he worked his way into a higher-leverage role in front of closer Felipe Vazquez.
It's also tough news for a bullpen that looked like one of the club's greatest strengths heading into next season. Santana would have joined an imposing back-end group that will still include Vazquez and setup men Keone Kela, Kyle Crick and Richard Rodriguez.
The Pirates acquired Kela from the Rangers before the non-waiver Trade Deadline to bolster their bullpen depth over the next three years. Kela, who is under club control for the next two years, was shut down earlier this month due to his "high-leverage workload this year compared to the previous two seasons," general manager Neal Huntington said in a statement on Sept. 15.
Trainer's room
• Infielder Jungho Kang (left wrist surgery) played nine innings in the instructional league on Wednesday in Bradenton, Fla., Tomczyk said, and reported back with "no complaints." Kang is scheduled to take more at-bats on Thursday.
• Right fielder Gregory Polanco (shoulder surgery) reported to the Pirate City complex for an assessment. His rehabilitation will take place in Bradenton and Miami for the next eight weeks.
"We're going to keep close ties on him," Tomczyk said. "He's met with our performance nutritionist, our performance team, our mental conditioning staff, so we're getting the rehab process started."
• Tomczyk said the Pirates are "optimistic" that right-hander Joe Musgrove will not need surgery after six weeks of rest. Musgrove was shut down on Saturday with a stress reaction on the front of his pelvic bone and an abdominal wall muscle strain.
• Right-hander Chad Kuhl (Tommy John surgery) has returned home to Delaware to begin his rehab.
• Right-hander Jameson Taillon will make his career-high 32nd and final start of the season on Saturday, manager Clint Hurdle said.
"It was just having a conversation with him at this point in time of the season, how he felt," Hurdle said. "I thought he was due the respect of having a conversation, not just taking for granted that he's pushed past a lot of markers. He feels confident and convicted on going post to post. He's in a place to do it."