Arsenal manager Arsene Wenger said he was “worried” about his side’s recent results on a night where three title challengers were beaten.
The Gunners’ 2-1 loss to Swansea leaves them third, six points adrift of leaders Leicester and Wenger says they “must get back to positive results”.
Tottenham missed the chance to go top of the table after defeat at West Ham.
And Leicester were helped further as Manchester City lost at Liverpool, leaving them 10 points adrift.
Wenger said his side’s loss of form “looks a bit” like a confidence issue after Ashley Williams scored late on to earn relegation-threatened Swansea a 2-1 win.
Arsenal have lost three games in a row for the first time since 2010 and injuries to defender Laurent Koscielny and goalkeeper Petr Cech could prove key when they meet Tottenham on Saturday.
“At the moment I am worrying about our results,” Wenger, 66, said. “At the moment we don’t dream. We have to be realistic and come back to what we do well, the basics.
“It’s a very disappointing result. The players are very down but we have to respond to that. I believe that we need to get back to positive results before we speak about the Championship which is at stake at the moment.”
Match of the Day pundit Alan Shearer: “Arsenal’s issues have been repeated over and over again, season after season. There is a lack of fight, lack of leadership, the same questions are hanging over them. You’d think they would come out and make a statement [after Sunday’s defeat at Manchester United] but it wasn’t there. Again.”
Leicester’s 2-2 home draw against West Bromwich Albion on Tuesday gave Spurs the chance to top the table in the month of March for the first time since 1964.
But they looked a shadow of the side who had won six successive Premier League games and Michail Antonio’s single strike secured victory for the Hammers.
“Was it nerves? No,” Spurs boss Mauricio Pochettino, 44, said.
“I think we made some mistakes that we normally don’t make. We started badly, conceded a goal and West Ham played better than us.
“We were poor. We know. We are very disappointed. But the way the players fought in the second half was fantastic.”
Match of the Day pundit Alan Shearer: “Spurs lacked energy, they had no spark, their passing was poor. West Ham were dominant all game. They overpowered Spurs. It was a thoroughly deserved three points.”
Fresh from their League Cup final win over Liverpool, Manchester City turned in a poor display at Anfield as goals from Adam Lallana, James Milner and Roberto Firmino sealed a 3-0 win.
City managed just four shots in the contest and ran 106km compared to Liverpool’s 115km.
“From the beginning I could see the team was not recovered from the last week,” Pellegrini, 62, said. “We played in the Champions League and League Cup final.
“I am not thinking about the title and not thinking not to qualify for the Champions League.
“I said always the team that wins title will be less than 80 points but I am not thinking about the title but to recover our performance.”
Manchester United boss Louis van Gaal, meanwhile, was in a very jovial mood after a 1-0 win over a Watford side, who created the better chances at Old Trafford.
Having seen his team’s Champions League chances written off and reportedly come close to the sack, United are now level on points with fourth-placed Manchester City, who have a game in hand but face United on 20 March.
“I have to give big compliments to our players because when it is physical and you can win at an important moment, when all our competitors are losing, it’s very important,” the Dutchman said.
“That’s the Premier League, the difference between clubs is so small, you can lose against every opponent, I think.
“We lost against Sunderland and there was a lot of criticism but that is the strength of the league and now you see we are closer to the fourth position, so now we are fighting for it.”
Asked by Match of the Day commentator Steve Wilson what he would say to those who had written off Van Gaal and his team, the United boss replied: “Maybe you were also one of them?” before laughing off into the night.
Match of the Day pundit Danny Murphy: “What’s amazing is that considering the negativity surrounding Man U they are level on points now with City. But Watford caused them all sorts of problems and they could have been in big trouble. None of us can predict what’s going to happen, that’s why we love it so much.”