De Gea howler huge blow for Man United's hopes in race for fourth as Chelsea draw at Old Trafford
Manchester United 1 Chelsea 1
David De Gea cost Manchester United again as the Red Devils' hopes of Champions League qualification were dealt a major blow.
United's three-game run without a goal was ended 11 minutes into the clash with Chelsea at Old Trafford as Juan Mata scored on his 31st birthday but another goalkeeping error allowed Marcos Alonso to equalise two minutes before half-time and the game ended 1-1.
Antonio Rudiger's speculative 35-yard shot was Chelsea's first effort on target and it should have been comfortable for De Gea but the Spaniard spilled the ball at Alonso's feet and he guided it in off the far post.
Ole Gunnar Solskjaer had given a firm rebuttal on Friday to suggestions he could take De Gea out of the firing line after a costly mistake against Manchester City on Wednesday and he will be faced with the same question again.
The draw means United remain three points behind fourth-placed Chelsea with only two games to go and with a substantially inferior goal difference.
Both managers rang the changes, with Solskjaer making five alterations to the team beaten in the derby on Wednesday.
Eric Bailly made a rare start in defence while Ander Herrera returned from a hamstring problem and Mata, Romelu Lukaku and Nemanja Matic also featured.
Rudiger and N'Golo Kante were both fit for Chelsea, with Alonso, Mateo Kovacic and Willian also in the starting line-up.
Luke Shaw produced an important clearance as Chelsea began strongly but the first clear chance went to United in the fourth minute.
Rudiger was caught under a long ball from Shaw and Romelu Lukaku held off the defender but Kepa Arrizabalaga was smartly off his line to smother the striker's shot.
Lukaku and Shaw were involved again seven minutes later, though, as United did take the lead.
Shaw began the move with a pass to Paul Pogba, who squared to Lukaku and his superbly-timed dink over the defence played in Shaw, who cut the ball back across the box for Mata.
The Spaniard had plenty to do with defenders on the line but he calmly picked his spot in the far corner to score against Chelsea for the first time since leaving Stamford Bridge in 2014.
It was the first goal United had managed from open play since Scott McTominay's effort in a 2-1 defeat by Wolves at the start of April.
Chelsea were having plenty of possession but without really threatening United, and a mix-up in their box could have been costly as Rudiger headed against the back of Alonso, but Cesar Azpilicueta was there to clear before the hosts could profit.
Moments later Bailly rose highest to meet a corner but headed just wide with Arrizabalaga beaten.
De Gea's error changed the whole feeling of the game going into half-time and Chelsea looked more dangerous in the early stages of the second half without managing to test the goalkeeper further.
The visitors were forced into a substitution in the 65th minute when Rudiger - who had fought off a knee problem to make the starting line-up - went down clutching his left leg and limped off to be replaced by Andreas Christensen.
United had to make two changes in quick succession, with Marcus Rashford succumbing to a shoulder issue that had bothered him since the first half and then, more seriously, Bailly twisting his right knee in a challenge.
The defender was able to limp off after lengthy treatment but it was clear he was in a lot of pain.
Alexis Sanchez and Marcos Rojo were the men to come on, and the defender was fortunate to see yellow rather than red after flying into a challenge on Willian, who also had to be substituted.
Amid all the stoppages, it was not surprising that the intensity had gone out of the game, and seven minutes were added to the end of the game.
It was United who created the first clear chance of the half when Rojo jumped to meet a corner but his header was cleared off the line by Pedro, while De Gea at least ended the game well with a block from Gonzalo Higuain.