Manchester United slipped to third in the Premier League as they were held to a frustrating goalless draw by Southampton at Old Trafford and their top two strikers both suffered potentially serious injuries.
Romelu Lukaku was carried off on a stretcher after a clash of heads in the first half, while manager Jose Mourinho later said back-up striker Zlatan Ibrahimovic would be out for a month with a knee injury.
United's other results over Christmas are 2-2 draws against Leicester and Burnley, and its main task might now be holding onto a place in the top four with Liverpool three points back in fourth.
"The pressure is coming from behind," United midfielder Paul Pogba said, "but we have to forget about everyone else and focus on ourselves."
Boos rang around Old Trafford at the final whistle and former players questioned United's players' attitude and Mourinho's ability to get the best out of his team.
"That is not United," former United midfielder Gordon Hill tweeted after the match. "I don't care what people say. Horrible."
The hosts had a strong penalty appeal turned down and had a late Paul Pogba goal disallowed for offside, causing manager Jose Maurinho to say it was a disappointing day.
Before he went off after a nasty clash of heads with Wesley Hoedt, Lukaku headed over a glorious early chance for United, while Jesse Lingard also put a header narrowly wide.
Lingard also appeared to be frustrated by the hand of Maya Yoshida in the box, but nothing was given by referee Craig Pawson.
The Lukaku injury came less than 10 minutes into the game. The striker was carried off on a stretcher and wearing an oxygen mask after a stoppage of around five minutes.
Mourinho could not give any further details on Lukaku's condition but appeared to rule him out of Monday's game against his former club Everton and Friday's FA Cup tie at home to Derby County.
"To leave the pitch the way he did, and we didn't think twice about making that decision immediately, is because there is a problem not just for today but the next two matches I would say for sure," he said.
Mourinho was also frustrated his side were denied a spot-kick by Pawson after the Yoshida incident.
"I think it is also a frustrating afternoon for Craig because he's a fantastic referee, one of the most promising referees in Europe. I feel bad for him," said Mourinho.
"We missed easy chances but there was a clear penalty that wasn't given.
"I'm happy with the players' attitude and the players' desires."