BALTIMORE -- Orioles second baseman Brian Roberts will be sidelined three to four weeks with a ruptured tendon behind his right knee.
The injury, to the part of the knee typically used to repair a torn ACL, will not require surgery. Roberts was placed on the 15-day disabled list prior to Friday's home opener against the Twins with what was termed a right hamstring strain. Infielder Yamaico Navarro took Roberts' place on the active roster.
"[It's] actually good news," manager Buck Showaler said after the Orioles' 9-5 win over the Twins. "Considering that's the same tendon/area they take out of your leg for Tommy John [surgery], which tells you some doctors think it's not a part of your body you necessarily have to have in that area. We are hopeful in a three to four week period we will get him back. I was talking to Brian about trying to be upbeat. This is really good news, kind of like Wilson [Betemit]."
Roberts, who exited Thursday's game in the top of the ninth inning, underwent an MRI on Friday morning. The 35-year-old had held out hope that he would avoid the DL.
"This is something that regardless of what [the MRI] says, will heal, and he will play for us again," Showalter said. "We hope that Alexi [Casilla] and Ryan [Flaherty] can help us hold down the fort until he comes back. We've had to do it before. It's just another challenge but not only [for] Brian, but our team."
Roberts, who will leave on Sunday to go back to the team's spring facility in Sarasota, Fla., walked out from the home dugout instead of jogging down the orange carpet during Friday's pregame ceremony and was greeted with applause.
"[It was] probably good for him, but also kind of he'd like to be a part of it more playing," Showalter said. "I had to kind of nudge him about going out for introductions. I think he really wanted to be a part of it. I felt real confident in our fans that they would respond like they did."
The injury occurred when Roberts stole second base at Tropicana Field on Thursday and grabbed the back of his right knee in pain when he came up. He was helped off the field by head athletic trainer Richard Bancells and first-base coach Wayne Kirby, putting a damper on the Orioles' series win.
Roberts, who has dealt with a host of injuries and hasn't played a full season since 2009, said Thursday night that he had never had a hamstring injury and was understandably down.
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 his old self in the field and at the plate. He hit .417 in three games, batting ninth for the Orioles in their season-opening series, and had been looking forward to suiting up for Friday's home opener.
Instead, Flaherty got the start at second base against Twins righty Liam Hendriks with Casilla also figuring to get more playing time there.
"Everyone knows what I can do," said Casilla, who ran for Roberts after he got hurt Thursday. "I can play short, second, even third. I'll be ready for anything. I just want to help the team."
In addition, Casilla's played with J.J. Hardy before, which will help the new Oriole settle into his spot at second base.
Navarro drove up from Triple-A Norfolk Thursday night. The 25-year old infielder has played a total of 71 games in the Major Leagues, seeing time with the Pirates, Red Sox and Royals.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. Jeff Seidel contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.