Before the Cubs closed out their series with the Marlins in Miami Wednesday evening, they swapped out young right-handers in the bullpen.

Keegan Thompson was activated off the Injured List and Jeremiah Estrada was optioned to Triple-A Iowa.

Thompson, 27, has missed more than a month with low back tightness. He began the year in the bullpen before moving into the rotation prior to his injury. The Cubs plan to use Thompson out of the bullpen over the final two weeks of the season.

He pitched the final 3 innings of Wednesday’s 4-3 win over the Marlins, striking out 6 batters and allowing only 1 hit and 1 walk.

Right now, the Cubs are rolling with a 6-man rotation though veteran southpaw Drew Smyly was skipped due to shoulder fatigue:

Marcus Stroman will start tomorrow for the #Cubs. Drew Smyly will be pushed back due to shoulder fatigue. Not expected to be anything serious. Just want to give him extra time.

— Taylor McGregor (@Taylor_McGregor) September 20, 2022

Here are the Cubs’ projected starters for the weekend series in Pittsburgh:

Thursday — Hayden Wesneski (2nd career start)
Friday — Javier Assad
Saturday — Wade Miley
Sunday — Adrian Sampson

In 26 games this season (including Wednesday’s outing), Thompson is 10-5 with a 3.86 ERA, 1.30 WHIP and 97 strikeouts in 107.1 innings. He has been one of the bright spots of the Cubs’ season and figures to be a big part of the pitching staff in 2023 — as a starter or a multi-inning reliever.

“He’s had a really nice season up to this point,” David Ross told reporters in Miami. “Trying to take care of him, his body, get him back full strength from a stamina standpoint to just building his body back up in the down time, making sure he’s completely healthy was a top priority for us.

“He feels good, he wants to go out there and help his team win. He’s worked really hard in the weight room, in the training room and we’re happy to have him back.”

Estrada, 23, is one of the Cubs’ top pitching prospects (coming it at No. 24 on Lance Brozdowski’s midseason rankings). He was called up last month and made his MLB debut on Aug. 30.

He carries a 3.18 ERA with 8 strikeouts in 5.2 innings. He threw 2 shutout innings in Monday night’s game against the Marlins, tallying 4 whiffs.

Estrada posted dominant numbers in the minor leagues with a 1.30 ERA in 48.1 innings across three different levels this season. He did not allow a run with Triple-A Iowa, striking out 12 batters in 6 innings.

Ross sees a lot of potential in Estrada but also room for growth.

“The fastball is real, maybe one of our best fastballs in our organization,” Ross told Taylor McGregor Tuesday night. “What excites me is that he’s still very unpolished. The breaking ball hasn’t really shown up yet. It’s not a weapon for him yet.

“He’s still got a lot of improvement that’s ahead of him that he’s capable of doing. … That swing-and-miss is real and hard to find. When you have a fastball like he does with real carry and at the velocities of 97, 98 – he gets above the barrel for a lot of those hitters. A lot of bad swings [Monday]. He’s exciting just ’cause I don’t even think he’s touched his potential.”