Update 1:07 PM ET, Friday: Roberts will be out 3-4 weeks with a ruptured ligament behind his knee, reports Brittany Ghiroli of MLB.com.
Surgery will not be needed for the 35-year old second baseman.
Yamaico Navarro has been called up from Triple-A Norfolk to replace Roberts' spot, the Orioles announced via Twitter.
Update 6:49 ET: The Orioles are now saying that it is Roberts' hamstring, reports Roch Kubatko of MASN. Roberts told reporters that he felt a pop in the back of his knee.
The Orioles second baseman singled and stole second base, but came up and grabbed his right knee in pain and was helped off the field by head athletic trainer Richard Bancells and first base coach Wayne Kirby.
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Roberts has missed a huge chunk of the past few seasons with various injuries, and for the aging middle infielder this may be the final straw if it is serious enough. It took him this long to get healthy again, and if he has to miss significant time it will be a major blow to both him and Baltimore.
Roberts had to be helped off the field by the Orioles' training staff, which certainly is never a good sign.
At the time of the injury, the Orioles were winning 6-2 in the top of the ninth inning against the Tampa Bay Rays. The stolen base is his first of the season.
Roberts has been a very productive player throughout his career, and he even made an All Star team as recently as 2007. It is a shame to see a player with so much talent have to deal with such poor injury luck.