Manchester United were beaten 3-2 by Brighton on Sunday afternoon.
Sergio Aguero netted his 13th hat trick for Manchester City as the champion made light of the absence of the injured Kevin De Bruyne to thrash Huddersfield Town 6-1 and move joint top of the Premier League.
Mourinho's side were blown away on the south-coast as Brighton scored twice in two minutes thanks to goals from Glenn Murray and Shane Duffy midway through the first half. As for United, Romelu Lukaku and Paul Pogba were on the score sheet.
Both signed by Mourinho for a combined fee of £60 million, they have started the season as first choice but it would be no surprise if they were both sat in the stands when Tottenham turn up at Old Trafford on August 27.
A surly Mourinho spent the build-up to this clash choosing to criticise rivals Manchester City's fly-on-the-wall documentary.
If you believe all the transfer stories in the summer, United were linked with 160 new players and signed three of them.
His relationship with Jose Mourinho is not good right now, despite the Portuguese coach praising his "monster" performance in last week's 2-1 win over Leicester.
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"I'm sure Eden will be with us for this season". "In those 15 minutes, we were not able to do this, and so we were in trouble". But he's a great player. "He needs to do that in each match - be demanding for us".
And Premier League hero Shearer has hit out at Mourinho, claiming the United boss is jealous of City's success.
"They had more hunger than us and I think they showed that, but our attitude wasn't right".
In the second half, he was deployed in a deeper position after Pereira and Mata were replaced by attacking England duo Jesse Lingard and Marcus Rashford.
When United also lost on their last visit to Brighton in May, Mourinho lambasted those handed their chance to fight for a place in the FA Cup final in one of a series of public tirades against his players.
Favourite for the sack with many bookmakers, Mourinho was visually apoplectic at some of his players' defending at the Amex Stadium with Eric Bailly coming in for significant criticism during United's shoddy defensive display.
Mourinho will now demand an instant reaction when United hosts Tottenham in its next game.
Pep Guardiola's men are looking to secure back-to-back titles - and City already look unstoppable once again.
Unbeaten Watford are alongside City as joint leaders after an eye-catching win at Burnley, who have gone seven league games without a win, following early second half strikes from captain Troy Deeney and Will Hughes.