Roberts stole second base but came up and grabbed the back of his right knee in pain and was helped off the field by head athletic trainer Richard Bancells and first base coach Wayne Kirby. The 35-year-old Roberts, who has dealt with a host of injuries and has not played a full season since 2009, said it was his first hamstring injury, and he was understandably down about the injury.
Asked how he felt mentally, Roberts said: "Not too great. I don't know. I don't have a whole lot of words for it right now. Frustrated, but we'll get the results and hopefully move forward."
Roberts worked hard to be a full-go this spring and had looked to be more of his old self in the field and at the plate. He is hitting .417 in three games, batting ninth for the Orioles in their season-opening series, and had been looking forward to suiting up in Friday's home opener.
"Dr. [John] Wilckens will see him tomorrow," manager Buck Showalter said. "That's a quick turnaround. Not going to say he's going to be able to play tomorrow. We'll reassess it tomorrow and see where we are. He's in some discomfort."
While it's still early to be speculating on a possible trip to the disabled list for Roberts, the Orioles do need to make a roster move to clear a spot for starter Chris Tillman on Saturday. Should Roberts be sidelined, Alexi Casilla -- who took over Thursday -- figures to get the bulk of the playing time at second base.
"He's been struggling for the past three years," Thursday starter Miguel Gonzalez said of Roberts. "And he's a great, great teammate. Battles, plays hard and that's what you want in a teammate; I hope he comes back quickly. And I think he will. He said he's hurting a little bit, but he will be back."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.