Right-hander Casey Mize expressed frustration when the Detroit Tigers transferred him to the 60-day injured list. He wants to pitch for the Tigers as soon as possible, but the Tigers forced a longer-than-expected return from a left hamstring strain.

The Tigers won't be able to activate Mize from the injured list until Aug. 30 because of the injured-list transaction, even though he began his rehab assignment Thursday with Triple-A Toledo.

Mize hasn't pitched for the Tigers since June 30.

He was placed on the injured list July 1.

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"We want to get him ready as fast as possible," manager A.J. Hinch said before Sunday's game. "Starting pitchers are really hard to plan out because to build up them up to have five (innings) and 75 (pitches), or six and 85, where they can have a normal start, that's like a three-and-a-half week process, given the time off in between, and even when they throw their last rehab, say it's in the August 20-25 range, there's still a five-day period after that before they will be usable in the big leagues."

Here's what happened at the end of July: The Tigers had to open a spot on the 40-man roster for left-handed reliever Bryan Sammons because they needed a healthy arm, but instead of cutting lefty reliever Eason Lucas or refusing to acquire righty reliever Ricky Vanasco, the Tigers transferred Mize from the 15-day injured list to the 60-day injured list, thus clearing space on the 40-man roster for Sammons.

Mize wasn't pleased.

"Before, I went to Casey and talked to him, just about the timing," Hinch said Tuesday on MLB Network Radio's "Power Alley," hosted by Mike Ferrin and Jim Duquette. "He's been out such a long time. It really is going to be a spring training build up. Given the time of the year, we're not going to speed it up. We're not going to risk tweaking something and all of a sudden he misses the year because these innings are really important for this year, they're also really important for a baseline moving forward. We told him we were going to be a little bit slow."

In the 2024 season, Mize has a 4.23 ERA with 21 walks and 58 strikeouts across 78⅔ innings in 16 starts. The 27-year-old missed all of 2023 recovering from elbow surgery and back surgery in 2022, so he hasn't thrown this many innings since 2021.

The Tigers selected Mize with the No. 1 overall pick in the 2018 draft.

"As we needed a roster spot, I explained to him, 'If you were going to be ready like the last week of August, if you push it back a couple of games, that's very important for our team now,'" Hinch continued on MLB Network Radio. "Afterwards, it's just the reality. You're going to be ready on the 20th or 25th, and you need another five days before you can pitch anyway. It wasn't really going to impact where he was, and given that we needed relief work by Bryan Sammons, and we needed pitcher after pitcher, I didn't really want to think about August 25-30. I wanted to think about today. We needed innings today."

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As of now, the Tigers only have two starting pitchers — ace Tarik Skubal and rookie Keider Montero — in the starting rotation, along with 11 pitchers in the bullpen, including long relievers Sammons, Kenta Maeda and Brant Hurter.

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Mize isn't eligible to join Skubal and Montero in the rotation until Aug. 30, which is the opener of a three-game series against the Boston Red Sox at Comerica Park.

After Thursday's start, Mize appears lined up to pitch Aug. 13, Aug. 18 and Aug. 24 for the Mud Hens before joining the Tigers. His innings in his first rehab start will be dictated by his pitch count.

The Tigers hope Mize will pitch multiple innings Thursday for Triple-A Toledo against the Jacksonville Jumbo Shrimp, an affiliate of the Miami Marlins, at Fifth Third Field.

Contact Evan Petzold at epetzold@freepress.com or follow him @EvanPetzold.

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This article originally appeared on Detroit Free Press: Tigers' Casey Mize starts rehab assignment, still out until Aug. 30