Manchester United's Marcus Rashford is staying positive as he aims for a safe return from a back injury, says Ole Gunnar Solskjaer.

Rashford is set to miss at least six weeks after suffering a stress fracture in his back in United's FA Cup victory over Wolves on Wednesday.

His injury leaves United without their leading scorer and attacking talisman, with Rashford having netted 19 goals across all competitions so far this season.

Asked to provide an update on Rashford ahead of United's encounter with Burnley, Solskjaer said the 22-year-old is in good spirits, though could put no definitive timescale on his return.

"He won't be fit for this game, for sure. He'll be out for a while, he'll get the time he needs to recover," Solskjaer told a news conference.

"Marcus is good, he's a positive guy and he knows this is not what he wanted but he's always positive.

"He wants to get back as quickly as possible but as safely as possible, so we'll give him that time and when he feels ready and medically we've cleared him, he'll be back."

Reports had suggested Rashford had been playing through the pain of a single stress fracture for some time prior to aggravating the issue in the match against Wolves, but Solskjaer insisted the England forward was not carrying an injury. 

"It's not one he's had before, no," Solskjaer said. "He complained a little bit after the last time we played Burnley. 

"We managed it as well as we could. He had some days off with treatment, we took him off when we could, he didn't start every game and then suddenly this was a new injury, so he didn't have any injuries before then."

United academy players D'Mani Mellor and Largie Ramazani have been tipped as possible replacements for Rashford, though Solskjaer suggested it was not the right time for the youngsters to come in.

Instead, Mason Greenwood looks set to continue his development, while Solskjaer hinted United may look to bring in a player this month.

"Of course, we're always looking at improving the squad and seeing if there's anything out there, but nothing that I can talk about now," he said.

"It might be too soon for [Mellor and Ramazani] yet. Of course, Mason is going to get more chances now. Juan [Mata] will have to step up again, so there'll be more chances for the ones we have in the squad.

"We know we're stretched with numbers and the injuries we've had, but we'll cope with that."