Carson Fulmer or Hector Santiago? White Sox going down to the wire on key call

GLENDALE, Ariz. — On Saturday, White Sox manager Rick Renteria made it official that veteran right-hander James Shields will start on opening day in Kansas City. So that’s finally settled, which is nice.

On Sunday, though, Renteria wouldn’t give on the subject of his fifth starter, probably the biggest open question the Sox have with seven spring-training games to go.

Will it be right-hander Carson Fulmer or left-hander Hector Santiago?

Fulmer, with all of five big-league starts under his belt, has been a mess this spring. Allowing a home run per inning, his ERA at 18.90 and the rest of his numbers similarly atrocious, the 24-year-old has two more spring starts — the first of them Monday against the Diamondbacks — in which to build some momentum.

‘‘We’re going to allow Fulmer to be who he is and see if he can have what everybody hopes to be a positive outing,’’ Renteria said. ‘‘We believe we have a guy who has the capability of pitching in the big leagues successfully. I think we’re at a point in time right now where we’re going to be able to evaluate over the next couple of starts to determine what we’re going to do.’’

Some would say the answer to that is readily apparent: Just give the ball to Santiago and see if he can find the level he pitched at in 2015 and 2016, when he won a combined 22 games for the Angels and Twins.

Santiago, who began his big-league career with the Sox, languished in free agency before the Sox signed him to a minor-league contract just as spring training was starting. If all worked out, the idea was that he might get an opportunity to fill the long-man role out of the bullpen.

But with left-hander Carlos Rodon out indefinitely, the Sox need someone they can believe in at the back of the rotation. Would experiencing intense growing pains at the big-league level be helpful to Fulmer’s development? Santiago — who has allowed one run in 10 spring innings — has been generous with his time and encouragement to Fulmer, but he also happily would accept another shot at a starting role.

‘‘[In] the clubhouse and all around off the field, I try to be a good teammate,’’ he said. ‘‘But when you’re in between the lines, you’ve got to go out there and do your job and compete for yourself.’’

Santiago has started once and pitched three times in relief — each time in a game started by Fulmer. In other words, they’re on the same pitching schedule. It certainly suggests Santiago remains in play for a starting role. Twice when asked about Santiago, Renteria gave an answer about Fulmer.

‘‘As far as I’m concerned right now, [Fulmer] went out and had a nice last month of [2017] for us, really improved, and we think he can build on that,’’ Renteria said. ‘‘We’ll take the spring with a grain of salt, but we’ll use some of it to determine what, exactly, that we need to do to help him continue to improve.’’

During a rebuild, you’re supposed to have time on your side. But Renteria will have to render a Fulmer-or-Santiago decision soon. Santiago is ready if called upon.

‘‘Overall, my career stats as a starter have been pretty good,’’ he said. ‘‘So I think I’ve gained the confidence of my staff and teammates to be able to go out there and start.’’

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Email: sgreenberg@suntimes.com