The Cubs parted ways with one of the key members of their 2024 bullpen.

The team announced they had designated right-hander Tyson Miller for assignment on Thursday. The 29-year-old was on a rehab assignment with the Iowa Cubs and was on the 60-day injured list.

Miller, who was originally drafted by the Cubs in the fourth round of the 2016 draft, was acquired via trade last May after he had been designated for assignment by the Seattle Mariners. It was one of the Cubs’ early moves to try and rectify their early season bullpen woes.

The move paid off.

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He posted a 2.15 ERA and 0.81 WHIP in 50.1 innings across 49 appearances for the Cubs last season. But bullpen arms can be volatile – and in Miller’s case, injury was a cause of that. He was named to the team’s Opening Day, 26-man roster for the Tokyo Series, but did not appear in the two-game set against the Dodgers. He landed on the IL with a left hip impingement after the team returned stateside.

He was sent on a rehab assignment to Triple-A Iowa in mid-April and was hit by a comebacker on May 9. That prompted the Cubs to transfer him to the 60-day IL when they selected the contract of top prospect Moisés Ballesteros.

Miller returned to pitching for Iowa on May 21 and pitched 4.1 scoreless innings across four outings with four walks and two strikeouts. He had a 2.77 ERA in 13 innings with Iowa this season.

The Cubs clearly felt better with their current in-house relief options than bringing Miller back to the majors. The Cubs’ eight-man reliever corps features seven players without minor league options – right-hander Daniel Palencia is the only one who can be sent to the minors without passing through waivers. Palencia isn’t being optioned anytime soon after developing into a key leverage arm for manager Craig Counsell. The Cubs also would have had to make a 40-man roster move to accommodate Miller.

That meant he was expendable.

Miller debuted for the Cubs in 2020 appearing in two games in the pandemic-shortened season. He was designated for assignment the next season and has spent time in the big leagues with five other teams.