Arsenal risk being cut adrift in the Premier League title race after a humiliating 6-0 defeat at leaders Chelsea in Arsene Wenger's 1000th match as manager on Saturday.
Wenger described the result as "one of the worst days" of his career and his misery was compounded by handsome victories for Liverpool and Manchester City that saw his side slump to fourth place in the table.
Luis Suarez scored a hat-trick as Liverpool won 6-3 at Cardiff City to move to within four points of Chelsea, while City are two points further back - but with three games in hand - after Yaya Toure also claimed a treble in a 5-0 win over Fulham.
Meanwhile, Manchester United striker Wayne Rooney scored an astonishing 58-yard lob in a 2-0 win at West Ham United.
Arsenal are now seven points below Chelsea, albeit with a game in hand, after Wenger's side were blown away by a flurry of first-half goals from Samuel Eto'o, Andre Schurrle, Eden Hazard and Oscar at Stamford Bridge.
"This defeat is my fault. I take full responsibility for it," said a crestfallen Wenger, who then chose not to attend his post-match press conference.
"I don't think there's too much need to talk about the mistakes we made. We got a good hiding today."
Mourinho, whose side had crashed to a 1-0 defeat at Aston Villa last weekend, said: "At 2-0 after seven minutes, the game is over. We were too strong."
Chelsea remain top, but Liverpool are hot on their heels, and have a game in hand, after twice coming from behind to overwhelm second-bottom Cardiff in south Wales.
Ole Gunnar Solskjaer's side threatened to pull off an upset by going ahead through Jordon Mutch in the ninth minute and then retaking the lead through Fraizer Campbell after Suarez had equalised.
Liverpool centre-back Martin Skrtel equalised in the 41st minute, however, and Suarez's two second-half strikes, allied to goals from Skrtel and Daniel Sturridge, secured a sixth successive victory for Liverpool, with Mutch replying for Cardiff.
Suarez now has 28 league goals for the season, just three short of the record for a 38-game campaign.
"His determination, his desire, his will is at such a big level. He is a world-class player who is enjoying his football, and long may it continue," said Liverpool manager Brendan Rodgers.
City moved above Arsenal into third place after Toure's treble helped to put paid to bottom club Fulham, who had defender Fernando Amorebieta sent off early in the second period.
Norwich City were the only team in the bottom seven not to lose on Saturday, winning 2-0 at home to Sunderland through goals from Robert Snodgrass and Alexander Tettey to climb seven points clear of the bottom three.
