The midfielder caught his studs in the turf during the 1-1 draw with Derby County and had to be stretchered off with suspected ligament damage.
Initial scans have proved inconclusive, manager Gary Bowyer revealed, and the 22-year-old is expected to miss a lengthy period of time.
Bowyer told the club's official website: "He had a scan yesterday and he has got to have it re-scanned later on in the week.
"Like I said at the time, it probably looks like it will be a little bit longer than a couple of weeks that is for sure.
"The lad is obviously gutted with the injury because he was playing the best football of his life, but if anybody knows Marshy you can't keep him quiet for a while."
However, Joshua King is back in the Rovers squad for tomorrow's game against Barnsley after missing the match against Derby.