The powerful Gloucester back-rower, who impressed on the British & Irish Lions tour of New Zealand over the summer, has only played once this season against Leicester Tigers on November 4.
A niggling back problem has been behind his lack of action and now Gloucester boss Johan Ackermann has revealed there has been another setback in training refusing to put a timescale upon his return
"It's not the same injury, but it is similar symptoms that we just manage and treat," said Ackermann.
"They don't want to give us a timeline because it just adds pressure to the player, but obviously we've backed off a bit with him coming back into games.
"He's doing his rehab, he's doing his running - all those things to get him back, and once they feel they've built him up enough then they will get him back on the field."