Doncaster coach Tony Miller is missing Danny Cowling (suspended) and Chris Spurr (finger), but Kyle Kesik could come back into contention after being rested for last week’s match against Sheffield Eagles.
But Morrison remains in upbeat mood ahead of Sunday’s Kingstone Press Championship do-or-die play-off.
Morrison said: “We had to start our finals series three weeks ago. We needed to win each week just to stay alive, and we’ve had a really good buzz about the place. Everybody’s relaxed and ripping in.
“It’s hard to get that finals football mentality, but we’ve had it there for a few weeks now and we want to keep that momentum going.”
He added: “We’re going to be at the bare bones, but we’ve shown in the last few weeks that people playing out of position have done a job for us.”