MESA, Ariz. -- The Cubs' signing of reliever Michael Fulmer was not exactly a mystery. The veteran went through his physical last week, has had a locker in the clubhouse for several days and even threw a bullpen session in uniform on Sunday morning.

Fulmer's one-year contract just did not get pushed across the official finish line until Monday. And he had a little fun with reporters when the time had come to stand at his locker and finally discuss his arrival with the North Siders.

"I feel like we've been playing hide and seek," Fulmer joked. "I think I win. You guys lose. But no, it feels good. I'm excited to be part of this group."

In order to add Fulmer to the 40-man roster, the Cubs placed reliever Codi Heuer on the 60-day injured list. Heuer is working his way back from undergoing Tommy John surgery on his right elbow in March 2022 and has resumed throwing off a mound three times per week.

After meeting with the media, Fulmer spotted Heuer as the fellow reliever strolled through the room. The new addition to the bullpen asked how Heuer's latest mound workout went. Heuer threw a bullpen session on Monday, sticking to just fastballs for the time being.

If everything goes according to plan, Heuer is hoping to rejoin the relief corps by June or July. Until then, the Cubs will be building a bullpen out of a mix of veterans and younger options, with no true closer at the end of the line. Fulmer and righty Brad Boxberger (both free-agent signees) will have chances in late-inning situations.

"I think it's making sure you're using guys in the right leverage spots, in the right pockets," manager David Ross said. "Where we feel like they match up the best and their stuff matches up the best is something that we try to lean on. And I think our pitching infrastructure here is really strong at identifying those things."

The bullpen currently sets up to feature Fulmer, Boxberger, Keegan Thompson, Adbert Alzolay, Rowan Wick and Brandon Hughes. Other options from the 40-man roster include Michael Rucker, Julian Merryweather, Jeremiah Estrada and Ryan Jensen. There is a lengthy list of non-roster candidates in camp, too.

Fulmer said he had a Zoom call with members of the Cubs' pitching group -- pitching coach Tommy Hottovy and director of pitching Craig Breslow, among others -- that went a long way. They talked about things to focus on over the offseason, whether or not the righty picked the Cubs in the end.

"Very genuine, very honest," said Fulmer, who added that he picked the brains of Andrew Chafin and Daniel Norris about their stints with Chicago. "I told them after the Zoom meeting that I wanted to be a Cub. I'm glad it worked out for everybody."

One thing Fulmer said the Cubs wanted to work on was developing a "bigger" breaking ball for this season. They went over grips with Fulmer on a version of the "sweeper" slider that other pitchers in camp have been honing. He went to work on it, and he has liked the early results in bullpen sessions.

Last season, Fulmer posted a 3.39 ERA with 61 strikeouts and 28 walks in 63 2/3 innings as a reliever for the Tigers and Twins. The 2016 American League Rookie of the Year as a starter with Detroit, Fulmer has spent the past two years converting to relief full-time after injuries and inconsistency earlier in his career.

Fulmer said he tells Tigers manager A.J. Hinch that "he saved my career by sending me to the bullpen."

Over the past two years combined, Fulmer has turned in a 2.98 ERA in 115 relief appearances. Last season, he held right-handed batters to a .544 OPS. Now, Fulmer is getting a chance to build on that successful transition to relief as a featured part of Chicago's bullpen.

"I'm just here to pitch, whatever role they decide," Fulmer said. "I think they're ready to get eyes on me in games and stuff, just like everybody else. So we'll go compete for whatever job we can compete for and be happy. As long as I'm pitching and healthy, I'm happy."