Atlanta Braves' Austin Riley heading to IL with knee ligament injury

Aug. 7 (UPI) -- Atlanta Braves rookie outfielder Austin Riley is heading to the injured list due to a knee injury.

Braves manager Brian Snitker told reporters Wednesday that Riley suffered ligament damage in his knee. The severity of the injury remains unknown.

"I don't know if they know 100 percent what's going on, but it's going to be enough to put him on the IL," Snitker said. "It's a knee ligament. I don't know the severity of it. We're going to have our doctors look at it [Thursday] and then probably get a second opinion."

League sources told ESPN and MLB.com that Riley sustained an injury while warming up to work out in the weight room before Tuesday's game against the Minnesota Twins. He felt discomfort while preparing to work out and had increased swelling in the knee Wednesday morning.

Riley has a .242 batting average with 17 home runs and 45 RBIs in 66 games this season. Since the start of July, he was hitting .169 with three homers while striking out in 45.1 percent of his 71 at-bats.

The Braves were expected to option Riley to Triple-A Gwinnett when Dansby Swanson returned from the injured list next week.