GLENDALE, Ariz. — Every time Carson Fulmer starts a spring-training game for the White Sox, Hector Santiago is always nearby.

Usually pitching in the same game and, on two occasions, cleaning up after Fulmer left a mess.

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If Fulmer hears Santiago’s footsteps, that’s because the 30-year-old left-hander with an All-Star season on his résumé has looked very good in his four Cactus League appearances, including one start.

“He is throwing really well,’’ manager Rick Renteria said.

And Fulmer isn’t, with 13 hits, including four home runs, and seven walks allowed in five innings (12.60 ERA) covering three starts. Fulmer, the Sox’ 2015 first-round draft choice, came to camp as the top candidate to be the fifth starter based in large part on a 1.56 ERA in his last four starts. It’s a job Santiago, signed as non-roster invitee protection, makes no bones about wanting.

“I’m trying to be a starter here,’’ Santiago said. “My whole career, somebody has been trying to take my spot. I’ve been in his shoes, and I know what he’s feeling — that feeling of trying to compete against somebody or that pressure.’’

Santiago was a 30th-round pick in 2006 who climbed his way up through the ranks of the Sox’ system, making the team coming out of spring training in 2012 as the closer. He would settle into the role of “Swiss Army Knife,’’ as former manager Robin Ventura called him, making four starts and pitching long and short relief.

After making 23 starts and 11 relief appearances with a 3.56 ERA for the Sox in 2013, Santiago was dealt to the Angels in a three-team trade that brought center fielder Adam Eaton to the South Side. Eaton would bring Lucas Giolito, Reynaldo Lopez and Dane Dunning in a trade with the Nationals, so Santiago can say he has done more than his share for the Sox’ rebuild.

Santiago became a solid starter with the Angels, making the All-Star team in 2015, when he finished with a career-high 180 innings to go with a 9-9 record and 3.59 ERA.

By 2017, though, an injury-plagued year turned Santiago into one of those veterans waiting all winter for a job. His mid-upper back is now good to go.

“Arm feels good, back feels good, just happy to be healthy and able to compete,’’ said Santiago, whose 93 mph velocity is two or three mph better than it was last spring. “You need that velocity when you’re mixing pitches and changing speeds, and it just wasn’t there last year.’’

This spring, Santiago has allowed one run in 10 innings with 10 strikeouts and three walks. He has allowed seven hits and little hard contact.

Fulmer still has time to get a grip on his spot and his place as a potential piece of the Sox’ future. But it’s time he steps forward.

“For his part, just go out there, and it’s his job to lose,’’ Santiago said.

Should Fulmer hold on, Santiago could go back to the Swiss Army Knife role and pitch multiple innings of relief — Renteria said Sunday that he wants multiple relievers able to pitch multiple innings — and be used as a spot starter. As a full-time starter, he could raise his value in a deal for a prospect at the trade deadline.

That’s the role he prefers.

“Carson’s not the enemy,’’ Santiago said. “We’ve had a good friendship. His job is to pitch well, and it’s in his hands. My job is to try to throw as many scoreless innings as I can out here, prove that I’m healthy and try to break with the team.

“That’s the game. There is always somebody behind you, somebody hungry, chasing your spot. You’re competing for your job or fighting to get back to the big leagues.’’

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