Orioles manager Buck Showalter said the team wasn't certain what was bothering Jones after he left Baltimore's 8-1 victory in the second inning. Jones started in center field as usual and struck out in his first at-bat before being replaced by Matt Angle, who pinch-hit for Jones in the second.
"After talking with a few people, he was feeling a little down and just weak," Showalter said. "Then after his first at-bat and everything, it didn't get any better. Didn't like what he was describing, so we decided to get him out of there and let the doctors take a look at him.
"They're still looking into it, haven't really been able to nail down. We just want to rule a lot of things out to be on the safe side. We're going to let them do some more tests at the hospital."
Showalter said he wasn't sure how long Jones would be at the hospital.
Jones has played in 124 of Baltimore's 126 games this season, batting .297 with 22 home runs and 77 RBI. Angle was recalled earlier in the day from Triple-A Norfolk when the Orioles designated slumping outfielder Felix Pie for assignment.