The Cubs continue to search for the right mix in the bullpen and on Tuesday, they reshuffled the relief corps.

The team placed left-handed reliever Brandon Hughes on the 15-day IL with left knee inflammation, retroactive to June 12. Jeremiah Estrada was also optioned to Triple-A Iowa and southpaw Anthony Kay was selected from Iowa.

To make room for Kay on the 40-man roster, Nick Burdi (appendectomy) was transferred to the 60-day IL. Miles Mastrobuoni also took Estrada’s spot on the roster, giving the Cubs an extra bench player for the start of the Pirates series.

This is Hughes’ third time on the IL with the same injury this season. The 27-year-old came into the season expecting to be one of the team’s high-leverage relievers and the main left-handed option out of the bullpen.

Instead, he has struggled to the tune of a 7.24 ERA and 1.61 WHIP in 17 outings (13.2 innings).

Hughes had some issues on the Cubs’ recent road trip, allowing 5 runs on 5 hits and 2 walks in his last 2 outings while recording only 2 outs.

“The knee has definitely been an issue,” David Ross said. “You saw how good he was last year when he feels healthy and being able to be in his mechanics in the right way. This year, it just hasn’t been for whatever reason — I think we would all point to the knee — but the production is not there, either.

“He recognizes that and wants to be better and keep having to get this thing calmed down a little bit and treated.”

Hughes was one of the great stories of 2022, making his debut in mid-May as a converted outfielder who made the switch to pitching as a minor leaguer in the Cubs system.

He quickly earned the trust of Ross and the Cubs, posting a 3.12 ERA, 1.09 WHIP, 8 saves and 8 holds in 57 games.

“He’s a big part of our future,” Ross said. “There’s a really good human being in there that’s trusted when he’s right and the way he competes is really special. I think my coaching staff, myself, the organization just loves when he’s right and going out there and competing — you trust him against anywhere. His splits are pretty neutral when he’s right. We just gotta get him back to being himself.”

Kay, 28, is a former 1st-round pick (31st overall) of the New York Mets in the 2016 Draft. He has spent parts of the last 4 seasons working as a starter and reliever for the Blue Jays, pitching to a 5.48 ERA in 70.2 innings.

The Cubs claimed Kay off waivers in December, then designated him for assignment in January to clear room on the 40-man roster. He was a non-roster invitee to Spring Training and began the year pitching for Triple-A Iowa.

Overall, Kay has been solid in the Iowa bullpen with a 4.50 ERA in 28 innings. He put together a dominant stretch right before the promotion, boasting a 1.08 ERA with 10 strikeouts over his last 8.1 innings.

“Kay is a guy we identified in the offseason as a guy that we thought we could improve a few things on a pitching infrastructure side,” Ross said. “Had gotten out righties pretty well and had struggled against lefties. The slider has played well down there.

“He’s done a nice job against righties and lefties down in Iowa and the opportunity presented itself and he was pitching the best. That’s kind of a credit to him and the work he’s put in to get better. We’ll use him as that lefty out of the ‘pen.”

Kay threw a perfect 9th inning Tuesday, closing out an 11-3 Cubs victory.

Like Hughes, Estrada struggled on the Cubs’ recent West Coast trip. The 24-year-old rookie allowed 6 runs in 3 appearances and saw his season ERA balloon to 6.75. He’ll head back to the minors to continue his development.

NOTES

—Justin Steele threw a bullpen Tuesday. The original plan was for him to face live hitters on the field but the rainy conditions moved the bullpen inside. If he continues to progress well from a left forearm strain, the Cubs could activate the southpaw as early as this weekend.

—Cody Bellinger (knee) began his rehab assignment Tuesday with Triple-A Iowa playing first base.

—Brad Boxberger threw a live BP in Arizona on Monday. He has been on the IL since May 14 with a right forearm strain.

—Edwin Ríos (groin strain) went through baseball activities Tuesday.