CHICAGO — Cubs fans held their collective breaths on Wednesday night.

The news that rookie Cade Horton was undergoing an MRI on his back after exiting Tuesday’s start after just three innings caused plenty of concern, with the playoffs less than a week away.

They receive a bit of a boost on Thursday, but he’s not fully in the clear, either.

“Cade is on track still,” Cubs manager Craig Counsell said on Thursday before the series finale against the New York Mets. “There’s some areas of concern in the ribs in the MRI. We’re going to continue to get more information on it and see where that leads us [and] use time on our side.

“But right now, Cade is a go.”

Counsell said the Cubs will have another physician give them an opinion on Horton’s MRI from Wednesday. That imaging left them unclear on whether the pain stems from the ribcage or the back, or if it has to do with connective tissue or muscles. Counsel and the Cubs still believe the injury stems from his illness and coughing, symptoms that arose when he fell ill last week after his start against the Pittsburgh Pirates.

“This is what we want to get more information about,” Counsell said. “That’s why we’re trying to make sure we know exactly what we’re treating, and I think as the days go on, rule stuff in and rule stuff out. And Cade progressing, we’ll kind of know how he’s feeling, and then we’ll be able to make a good decision.”

Horton will throw on Thursday after not doing so the last two days. That could be a big tell as to whether he’ll be able to go for next week’s three-game NL Wild Card series, which is officially against the San Diego Padres, after the Los Angeles Dodgers clinched the NL West division on Thursday afternoon.

The right-hander told Counsell – like he said in his postgame press conference on Tuesday – that he can pitch next week.

“He is experiencing some symptoms,” Counsell said. “The area of concern is the same place he was feeling the symptoms. There’s stuff to monitor, and we’ve got to cross some things still, but the fact that he’s going out to throw tomorrow – he’s optimistic he can pitch. Those are very good signs.”

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The Cubs are playing it safe by using the time that’s on their side. They won’t have to finalize a roster or starter until the series begins, and with four games to play, they don’t have to rush him into any decision.

“That’s why we want to make sure we use this time to let Cade tell us how he feels, let Cade show us how he feels,” Counsell said. “Consult with our doctors and let them make recommendations and get the best decision we can make.”

If he’s healthy, it’s clear he’s the Cubs’ best option to open the three-game series. Since the All-Star break, Horton has a 1.03 ERA and 0.78 WHIP in 12 starts across 61.1 innings. It’s the type of starter that you want headlining a playoff roster, if he’s healthy.

But if Horton can’t go, the Cubs will likely turn to one of Matthew Boyd or Shota Imanaga. Boyd started Wednesday’s win over the Mets, and Imanaga is slated to open Thursday’s contest.

“I think we have different plans, for sure,” Counsell said. “We met today on the playoff roster, so we’re at the phase where we’re starting to put plans into place, but we’re going to have multiple ones.

“We’ve got four baseball games left, which affects things.”