(CBS) As of Thursday mid-morning, the results of the MRI on Cubs catcher Willson Contreras after he suffered a hamstring injury in a loss Wednesday weren’t yet available, but the team is bracing for an extended absence.

“I don’t want to get ahead of it, but if it’s any type of significant hamstring strain, obviously that’s more than just a 10-day DL (trip),” Cubs president of baseball operations Theo Epstein said in an interview with Danny Parkins on 670 The Score on Thursday morning.

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Epstein refused to speculate on whether the injury could be season-ending, instead saying, “If it was a typical hamstring strain, the you’re usually looking at four to six weeks.” Such a timeframe would keep Contreras out until mid-to-late September. Contreras injured his hamstring running out a ground ball in the eighth inning at San Francisco on Wednesday.

The 25-year-old Contreras is hitting .274 with 21 homers, 70 RBIs and an .861 OPS. He leads all catchers in the game in homers and RBIs. Contreras has been particularly hot of late, hitting .324 with five homers and 13 RBIs in his past nine games.

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“Hoping for the best, obviously,” Epstein said. “He’s a key guy for us, carrying us offensively. Energy every single day, one of our best players. We want to keep it to a minimum, but we have to figure it out first, then come up with a plan.”

Epstein downplayed the notion that Contreras’ injury was caused by his heavy workload. With manager Joe Maddon wanting to keep Contreras’ hot bat in the lineup, Contreras was playing first base Wednesday instead of catcher. It was the seventh straight day he started, though not all of those have been at catcher.

“It’s important to remember to give him his rest, and I know that’s always on the forefront of Joe’s mind,” Epstein said. “It’s always easier in theory than reality, but it’s important, and this is another reminder why. It’s for everybody to get their rest, and Joe does it as well as anybody. This one, it happened, and we have to deal with it. Joe is a guy who gets criticized for giving guys too much rest, so I don’t think it’s fair to turn around and criticize him for not giving enough rest either.”

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With Contreras about to hit the disabled list, the Cubs are calling up catcher Victor Caratini from Tripe-A Iowa, Epstein confirmed. Alex Avila will be the primary catcher.