Montrae Holland's season is over
Loper, who plays guard and tackle, was cut Saturday to make room for running back Chauncey Washington. Loper has been cut by the Cowboys three times this year.
Holland, who could require surgery, suffered the injury in the fourth quarter of Saturday's 20-7 loss to Philadelphia.
"I got caught in a position where I tried to catch a guy and pull him back in front of me and it didn't work," Holland said. "So it wasn't the right position to be in."
Among the Cowboys' final cuts before the season started, Holland was brought back on Oct. 18 and started 10 games. He took over for rookie Bill Nagy, who fractured his ankle at New England. He will be a free agent after this season.
With Holland out, the Cowboys will turn to undrafted rookie Kevin Kowalski or veteran Derrick Dockery, who suffered a knee injury in his one start on Sept. 18 at San Francisco. Dockery has experience but he has been inactive the last two games.
Cowboys coach Jason Garrett didn't commit to either candidate Monday. If it is a matter of experience, Dockery, who is in his ninth season with 112 career starts, gets the edge.
"It's one of the reasons we like him and one of the reasons we signed him," Garrett said.
Both players say they'll be ready if needed.
"Coach does a really good job of keeping everyone prepared during the week because who knows how a game's going to go down?" Dockery said. "Injuries are a part of the game and you just have to be ready when you're number is called."
Kowalski got the call when Holland went down Saturday. He also filled in when Nagy was hurt and took over for Phil Costa two weeks ago against the Giants at center.
"Fortunately for me I'll be in the same role I had been in the last couple of weeks, so I don't think anything will be different," Kowalski said. "It's the same thing; just be prepared, not much to it."
Loper, out of Texas Tech, is a seven-year veteran but he has yet to be active for a game this year. He has played in 58 games with nine starts with Tennessee, Detroit and Oakland.
Todd Archer covers the Cowboys for ESPNDallas.com. ESPNDallas.com's Calvin Watkins contributed to this report.