Chris Smalling was left utterly frustrated as Manchester United slipped to a draw that "might as well have been a loss" given the size of the setback at this crucial stage of the season.

Defeat to swashbuckling league leaders Manchester City before the international break was followed by another gut punch on Saturday as struggling Crystal Palace left Old Trafford with a point.

United manager Jose Mourinho called into question some of his players' "heart" in the tepid 0-0 draw at home to a side that had not won a Premier League match in 10 weeks.

It leaves the Old Trafford giants facing a surely insurmountable 14-point gap to leaders City after 13 matches and an eye-watering seven points behind the Champions League spots – an understandable frustration for defender Smalling and his team-mates.

"I think we knew that sort of the period we had all the way to Christmas, there were so many home games that three points had to be a must," the centre-back said after drawing with Palace.

"So, whether it was a point or no points, it just might as well have been a loss.

"I think it's just about getting that first goal and then is sort of unlocks people and it makes them become a bit more open.

"Yeah, just utter frustration."

Smalling knows United were let-off as Patrick van Aanholt and Andros Townsend wasted glorious chances for Palace either side of half-time, but he felt "it shouldn't have got to that stage".

The 29-year-old was guilty of wasting a fine chance from a free-kick in the first half, with a frustrating afternoon epitomised by out-of-form Romelu Lukaku seeing a goal ruled for offside.

"Yeah, I think when it's going against you, you don't get those decisions," Smalling said.

"But we'll work hard again (on Sunday) because we know, given this run, that we can't have any more slip-ups at home again like this.

"I think we need to keep working hard as a team and creating those chances and ultimately finishing them and making sure that the games that we are dominate that we win."

Young Boys now arrive in a crunch Champions League tie on Tuesday evening, when Smalling wants to see 90 minutes of the kind of intensity that Mourinho felt was lacking in his side on Saturday.

"I thought the last 10 minutes there was added intensity that we maybe needed a bit earlier in the game," Smalling told MUTV.

"But we can't always leave it to the last minute and we needed to get that goal earlier.

"It is good to get back out in front of this crowd again (on Tuesday) and show a better performance."

Palace return to action when Burnley visit Selhurst Park next Saturday, when Mamadou Sakho wants to build on their promising performance in the north west.

"We can be proud of the job we did today," Sakho said on the Palace website. "Even if I think we could have won, I think that it was a positive point.

"We had quite a few occasions to score but today the squad made a good job defensively. We all defended together. It's a shame we couldn't score but it's positive as we created a few occasions we could have.

"The most important thing for me is if everyone gives 100 per cent for the squad.

"I think today we saw that, all the all the defenders all the midfielders and all the strikers made a big difference, we can be proud."