DETROIT -- Tigers right-hander Casey Mize will undergo Tommy John surgery to replace the ulnar collateral ligament in his right elbow, manager A.J. Hinch announced Friday.

Mize is expected to have the surgery next week. The rehab process will sideline the former No. 1 overall pick for the rest of this season and likely most of next season. The team should have a better idea of a timetable for recovery once he has the procedure.

Mize has been sidelined since mid-April, when he felt discomfort in his elbow following his second start of the season on April 14 at Kansas City. Tests conducted at the time and since have shown his UCL isn¡¯t torn, but a visit with specialist Dr. Keith Meister earlier this week resulted in a more complex test that measures elasticity.

¡°They call it a stress MRI, where they put his arm in a different position and see it from a different angle,¡± Hinch said.

What was initially described as a move out of an abundance of caution became more concerning when the right-hander struggled in a May 12 rehab start for Triple-A Toledo, allowing three runs on four hits over two-thirds of an inning. With follow-up exams and more visits with specialists still showing no tear, the recommendation from doctors was for Mize to rest his arm for another few weeks before resuming throwing.

¡°Obviously the first step is finding an accurate diagnosis,¡± Hinch said. ¡°I mean, I¡¯m not a doctor, but I know they¡¯re looking for tears and blood and issues that stand out. We can¡¯t be inside the elbow. And so, when they told us the ligament was intact, that gave us great confidence that there wasn¡¯t going to be a big problem.¡±

Mize restarted his throwing program last week, but felt less than full strength once he stretched out his throwing to 90 feet. That led to the visit with Dr. Meister and, ultimately, the additional test on the elbow.

¡°The fact that [the ligament] is intact, but yet still needs surgery, is part of the medical side that I have no idea about, but it¡¯s the reality,¡± Hinch said. ¡°I totally understand the definition of elasticity. I totally understand how a ligament can fail and still be intact. I¡¯ve learned more about this from my days as a manager than I ever knew prior. But it takes some time for differentiating between inflammation and actual injury. ¡­

¡°I¡¯ve heard of guys with 50-percent tears who are still pitching in the big leagues, so I don¡¯t think any of this is an exact science. You don¡¯t want to race to the surgery table despite how successful [the procedure] has been. The time lost is sometimes needed for recovery, but sometimes needed for diagnosis.¡±

Mize is the third member of the Tigers¡¯ young pitching corps to undergo Tommy John surgery while in the system. Alex Faedo, another Tigers first-round Draft pick, underwent surgery in January 2021 and returned to pitching in April. He made just four Minor League appearances before joining the Tigers' rotation, where he has become one of Detroit¡¯s most reliable starters. He¡¯s just the third pitcher since 1893 to throw at least five innings with two runs or fewer allowed in each of his first seven games.

Joey Wentz underwent Tommy John surgery in March 2020. He returned to game action in May of last season, made the rest of his starts on turn in the Minor Leagues, then made his Major League debut last month. He¡¯s currently sidelined with a neck issue that is affecting his shoulder.

Tarik Skubal, the shining star of the Tigers' rotation this season, underwent Tommy John surgery in 2016 while at the University of Seattle. He missed the entire 2017 college season before returning to pitch in 2018; the Tigers drafted him in the ninth round that year.

Spencer Turnbull, who came up before the young corps in 2018 and threw a no-hitter for the Tigers last year, is currently rehabbing from Tommy John surgery, which he underwent late last year. Michael Fulmer, an AL Rookie of the Year and All-Star as a starter, underwent surgery in Spring Training 2019.