How success as a reliever made Cubs’ Keegan Thompson a better starter

When Cubs right-hander Keegan Thompson looks back on his development during the past year, he’s most proud of the way he moved past his struggles at the end of last season.

“Being able to go through success and then failure and come out the other side is a big thing for me,” he said, “because you’re not going to have success every time [you go out].”

After a dominant start to the season, Thompson (6-0) is back in the rotation, at least for the time being. On Thursday, he allowed three runs in 5⅓ innings in a 7-5 victory against the Cardinals to open a five-game series at Wrigley Field.

Manager David Ross has talked plenty this season about how valuable Thompson is coming out of the bullpen for multiple innings every third day, rather than starting every fifth day. But the Cubs don’t have that luxury anymore. Their rotation is missing too many pieces.

Injuries to left-handers Wade Miley (strained left shoulder) and Drew Smyly (strained right oblique) in the past week put the team in a bind. Right-hander Alec Mills is nearing a return from the 60-day injured list, but he’s scheduled to make at least one more rehab start Tuesday.

So is Thompson’s addition to the rotation temporary as the Cubs sort through injuries or is it an opportunity to claim a more permanent spot?

“Could be all of the above,” pitching coach Tommy Hottovy said, adding that workload concerns could come into play later in the season. “I always love guys that get opportunities and seize them. I think if we’re building what we want to build in this organization, you should reward guys for pitching well and doing well.

“Now, with that being said, obviously as a team, you take into consideration what is the best option for everybody, and you don’t want to sacrifice one person for another, just because it’s a balance of all that.”

The Cubs tried to build up Thompson to start late last year. But after a series of short starts, they eventually shut him down for the last week of the season, citing shoulder inflammation.

This is different. Thompson already is built up just shy of starter’s innings and is pitching as well as anyone on the staff. Before Thursday, Thompson already had two five-inning starts. Entering play, Thompson’s 1.17 ERA out of the bullpen was the best among major-league relievers who have thrown at least 20 innings.

“Some of the stuff that I’ve heard him say is just about being an out-getter,” Ross said when asked how the reliever mindset has carried over to Thompson’s starts. “And simplifying it in that way, rather than setting some kind of tone or going out and trying to go seven innings and trying to pace yourself.”

Ross and Hottovy mentioned the impact of Thompson finding a routine that works for him.

Thompson prepared for spot starts just like he was coming out of the bullpen — no long toss on the field, warming up in the pen. He had started plenty of times in the minors but didn’t see a reason to change what had been working for a single outing.

Now it has turned into more than that.

“I can’t explain how valuable it is for a young guy to learn early that you don’t need to make extra throws just to get ready,” Hottovy said. “And would he have learned that if he was not in the bullpen before? You never know. But him being in the bullpen, [he learned] from some of the veteran guys about how they control their throwing programs and what it takes, and the work you put in between outings that makes it all pay off. So I think it’s been fun to watch.”

Against the Cardinals, Thompson didn’t have his best start of the year. He had set a high bar in his last two, throwing five scoreless innings against the Diamondbacks and holding the White Sox to one run. But he gave the Cubs a chance to win against the No. 2 team in the division.