Ole Gunnar Solskjaer admitted he is worried by Manchester United's goal drought following their 0-0 Premier League draw away to Crystal Palace.
United were held to their third successive scoreless draw across all competitions after firing another blank against Palace on Wednesday.
Solskjaer's faltering United produced another toothless display at Selhurst Park, where the Red Devils slipped 14 points adrift of runaway leaders Manchester City ahead of Sunday's derby.
United registered their sixth goalless Premier League draw of the season – the club's joint-most ever in a campaign, along with 2004-05 and 2016-17.
The Premier League giants have also drawn three consecutive matches 0-0 in all competitions for the first time since October 2015 under Louis van Gaal.
United manager Solskjaer conceded he is concerned post-match, with his team only a point clear of third-placed Leicester City through 27 matches.
"Of course it's a concern," Solskjaer told Match of the Day. "When you have three clean sheets in a row, that will help you win games but we haven't produced the quality.
"We just have to find a spark again, the quality again and try and win the games."
He added: "It's not good as you know if you want to move up the table, you need to win. You have to earn the right, you have to win tackles, you have to fight, you have to play passes better. We kept giving the ball away.
"The tempo was missing, once in a while it happens. It wasn't one of our best nights that's for sure.
"[Palace manager] Roy Hodgson always sets his teams up to be really hard to play against and it just showed again tonight.
"A couple of times when we had the tempo in the right positions, we created decent opportunities but I don't think we deserved anything more than one point."
United goalkeeper Dean Henderson started in the absence of star David de Gea, who was sidelined due to personal reasons.
Henderson impressed midweek, the England international staking his claim for a regular starting berth with a superb save to deny Patrick van Aanholt late in the second half.
"That's a Man Utd goalkeeper, sometimes you have to keep concentrating," Solskjaer told Sky Sports. "He's growing in that position. I thank him for one point and not zero."
Asked when De Gea will return, Solskjaer replied: "That's a private matter. It'll take the time it takes."