Manchester United manager Ole Gunnar Solskjaer said that Marcus Rashford's back injury could force the club to look at short-term options in January.
Rashford is facing a period of six weeks out plus rehab after Solskjaer confirmed the striker had suffered a double stress fracture in his back. The injury had kept Rashford out in the run-up to United's 2-0 loss to Liverpool on Sunday.
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"He's suffered a bad injury," Solskjaer told Sky Sports after the loss at Liverpool. "Yeah it's a stress fracture, it happened against Wolves [last week]. It's not happened before, it happened there and then.
"He'll be out for a while. He won't be back until after the mid-season break. Normally six weeks to heal, but I'm not a doctor, and then he needs rehab after that probably," he said.
Solskjaer also said United could look for a new striker as the window transfer window remains open until Jan. 31.
"We're always looking at chances to improve the squad -- with Marcus out for a while we have to look at it closely. We might look at some short-term deals. We are looking at numbers," he added.
Rashford's injury timeframe would see United face the prospect of playing up to eight league games without him before the March international break arrives. The club also remains alive in the FA Cup, Carabao Cup, and Europa League competitions.
The injury would also put Rashford in doubt for Gareth Southgate's England squad for the March friendlies against Italy and Denmark.
United are fifth in the Premier League, 30 points adrift of Liverpool after the loss on Sunday but Solskjaer was pleased with the display his side gave against the European champions.
"The players gave us everything. Today we hung on a bit at the start of second half, but the last 25-30 mins we pressed them and pushed them back. I'm disappointed with conceding from a corner and with the last kick - but very many positives," he said.
"I felt in the second half we performed really well against a good team and at a difficult place. We didn't have quality with our finishing or last pass. [Midfielder] Fred was absolutely top and [goalkeeper] David de Gea. As a team we worked together as a unit," he said.
Information from Reuters was used in this report.