Jameson Taillon‘s MRI results showed a “moderate strain” of his right calf, the veteran Chicago Cubs right-hander told reporters at Wrigley Field on Saturday morning.

Taillon was due to start Saturday against the Cardinals, but that spot now will be filled with a bullpen game opened by Drew Pomeranz.

Taillon hit the 15-day IL on Friday (retroactive to July 1) because the strain, which he sustained while running his usual post-bullpen sprints.

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“Unfortunately, I was on my last rep, and was literally almost done for the day,” Taillon told reporters. “I felt it kind of grab on me. … It just came out of nowhere.”

Cubs manager Craig Counsell told reporters Friday that he believed Taillon would “miss a pretty significant amount of time.” However, Taillon told reporters Saturday he is optimistic about his diagnosis.

“I think all in all, I’m pretty encouraged by knowing what it could have been,” he said. “It was the best case of what we (thought) it had the possibility of being.”

The Cubs still are evaluating what Taillon can do in his rehab. The right-hander told media that they’re “working through it.”

“We’re going to try to try to keep my arm conditioned, do some throwing off my knees,” he said. “Like stationary bike, upper body workouts, arm care. I think we’ll be able to stay pretty conditioned.”

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Taillon’s injury is another blow to a Cubs rotation that lost Justin Steele to season-ending surgery in April and only just got Shota Imanaga back from a hamstring strain that kept him sidelined for nearly two months.

“It’s been tough,” Taillon said. “We’ve been carried by the offense a lot this year — that helps. And then obviously, guys have stepped up and shown that they’re capable.”