MANCHESTER -- Manchester United's injury problems worsened on Saturday after Romelu Lukaku was stretchered off in the first half of the 0-0 draw with Southampton.

The striker was carried off after 13 minutes at Old Trafford following a clash of heads with Wesley Hoedt.

Manager Jose Mourinho told the BBC after the game that Lukaku would be "out of football for a while" while also revealing to BT Sport that United will be without Zlatan Ibrahimovic for the next month.

Lukaku, 24, was attended to by United's medical staff on the pitch for around six minutes before leaving on a stretcher wearing an oxygen mask, with Marcus Rashford coming on in his place.

Lukaku, who has scored four goals in his past 19 games and leads United with 10 Premier League goals this season, will now be a doubt for the trip to former club Everton on Monday.

Asked for Lukaku's availability for Monday, Mourinho told his news conference: "I don't know. I know that normally bad, bad news arrives immediately, and bad news didn't arrive. But to leave the pitch the way he did, we don't think twice to make that decision immediately.

"[It] is because there is a problem not just for today, but the next two matches, I would say for sure."

Romelu Lukaku was injured early in the first half on Saturday. Alex Livesey/Getty Images

If both Lukaku and Ibrahimovic are absent at Goodison Park, it will leave Mourinho with only Rashford and Anthony Martial as his recognised senior strikers.

United host Derby County in the FA Cup on Friday and then have 10 days off before facing Stoke City in the league. The Champions League round of 16 does not begin until Feb. 21 at Sevilla.

At a news conference on Friday, Mourinho had revealed Lukaku was "tired" but insisted that he was not in a position to rest the Belgian.

Lukaku had already missed a good chance before he was substituted on Saturday, heading over Juan Mata's cross from six yards.

Ibrahimovic was not in the squad against Southampton after starting his first Premier League game of the season against Burnley on Boxing Day.