GREEN BAY, Wis. -- If Eddie Lacy plays on Sunday against the Dallas Cowboys, he’ll do it without a full week of practice.

The Green Bay Packers running back won’t be on the field for Wednesday’s practice and instead will spend that part of the afternoon trying to strengthen his sprained left ankle. Lacy was unable to finish last Sunday night’s game against the New York Giants.

“He'll be in the rehab program today,” Packers coach Mike McCarthy said before Wednesday’s practice.

If Lacy can’t play against the Cowboys, the Packers might have to make a roster move. They have only two other backs on the roster -- struggling halfback James Starks, who is averaging just 1.8 yards per carry, and fullback Aaron Ripkowski, who despite his impressive 13-yard gain against the Giants is not a natural ball carrier.

McCarthy has used receivers Randall Cobb (five carries for 12 yards) and Ty Montgomery (two carries for 0 yards) out of the backfield this season with limited success.

They have one running back, rookie Don Jackson, on the practice squad, but Jackson did not play in a single preseason game this summer.

“We're still evaluating some things,” McCarthy said. “We'll see how Eddie moves around today in the rehab."

McCarthy indicated Monday that Lacy’s injury was not a long-term concern. Lacy sprained his right ankle in Week 2 last season but managed to play the next game.

In another injury-related issue, cornerback Sam Shields has taken another step in the concussion protocol. Shields has not played since Week 1, when he sustained his fourth career NFL concussion and his second in nine months, but McCarthy said Wednesday that Shields has been able to attend player meetings this week. McCarthy didn't say whether Shields has been cleared to practice yet.

“Getting better,” McCarthy said of Shields. “He’s in the meetings, so just saw him briefly today. Making progress is the report.”