CINCINNATI -- Reds starter Mat Latos had an MRI on his sore pitching forearm Saturday, a new problem that leaves him unsure of the next step in his recovery from a knee injury.

The right-hander had surgery to remove bone chips from his elbow after last season. His comeback was on schedule until he tore cartilage in his left knee while throwing in February. He had surgery the day the Reds opened camp.

Mat Latos, who had been plagued by injuries in 2014, was shut down after experiencing soreness in his forearm. Rob Leifheit/USA TODAY Sports

Latos was one of eight Reds who opened the season on the disabled list. The Reds were hoping to have him back by the middle of April, but his latest setback has pushed that back.

Latos was scratched from a rehab start in the minors this week because of elbow soreness. He threw on Friday but had to stop when his forearm became sore.

"Now it's the forearm," Latos said. "We thought we had it hammered out, but it came back on me."

The Reds were awaiting the test results before deciding the next step.

"Mat obviously didn't feel very good yesterday," manager Bryan Price said. "Everything started out fine, then he threw a pitch that bothered the inside of his right elbow and we're smart enough to know that we needed to shut him down.

"They're doing some testing to see if there's some swelling and tightness in the area. We're hoping that's all it is. We're optimistic that's it, but it is a step back."

Latos and closer Aroldis Chapman -- sidelined until at least May after being struck in the forehead by a line drive during spring training -- both rode in the city's opening day parade. Latos was frustrated that his arm began to bother him this week, extending his comeback.

"It's definitely bugging me," he said. "I'm definitely not getting a good night's sleep because of it."