Ole Gunnar Solskjaer says his Manchester United side need to find their "spark" again after they were held at Crystal Palace - a third goalless draw in a row for the visitors.
The Red Devils never really looked like scoring in a drab encounter at Selhurst Park, with their failure to win a blow to their already slim Premier League title hopes.
The result means Manchester United are 14 points behind leaders Manchester City, with the two sides meeting on Sunday.
Asked about his side's recent form, Solskjaer told BBC Sport: "Of course it's a concern.