United are set to be without Rashford for at least six weeks.
After the defeat to Liverpool, Solskjaer said: “He got a couple of knocks and jolts when he came on against Wolves and aggravated his back.
“It’s a stress fracture and it’s not something that’s happened before. It’s so unlucky for Marcus, he’ll be out for a while.
“He’s had some trouble before and we’re going to give him time to recover and rest before we put him back on the pitch. He won’t be back until after the mid-season break.
source: express.co.uk