(CBS) Bears receiver Markus Wheaton underwent an appendectomy Sunday morning, coach John Fox said.

There’s no timetable on Wheaton’s return to the field as the Bears continue training camp. The 26-year-old Wheaton signed a two-year deal with the Bears in the offseason after spending his first four seasons with the Steelers. He was projected to be a key part of the offense after Chicago lost receiver Alshon Jeffery in free agency.

“He had some stomach pains last night around 4 a.m., and our training staff did a good job getting him and he had the appendectomy at probably 9 o’clock this morning,” Fox told reporters. “They’ll keep him in the hospital tonight. It’s a scope type of procedure, but they caught it.

“It was inflamed, not ruptured, which is a good thing. So he’ll start that recovery process.”

Wheaton had three catches in 2016, when he played just three games because of a shoulder injury. He had 44 catches for 749 yards in 2015.