A couple of hours later, though, his Manchester United rival Mourinho, a general not used to humiliation, was forced to sit at a ground he once commanded and see his side ripped apart 4-0 as Chelsea produced one of the standout displays of the season at Stamford Bridge.
The results saw the battle at the summit hot up with only one point now separating the top five.
City lead Arsenal and Liverpool, with all three teams on 20 points, while Chelsea's triumph shoots them up to fifth, level on 19 with fourth-placed Tottenham Hotspur.
United, though, are now seventh on 14 points, one adrift of Everton, and with the pressure mounting on Mourinho, Wednesday's League Cup clash with Guardiola's men at Old Trafford takes on huge significance.
This was only the second time that a Mourinho team have conceded four goals in the Premier League.
For that to happen at Stamford Bridge was unthinkable for the Portuguese, who began the day with a hug from John Terry and ended it with what appeared some bitter words in the ear of his opposite number Antonio Conte.
United had just been ripped apart with goals from Pedro - the quickest in the Premier League this season - Gary Cahill, Eden Hazard and N'Golo Kante, and, as the clock ticked down, the Italian gesticulated to the crowd for even more noise.
Neither manager would reveal what was said in the post-match exchange but Conte said he was entitled to act as he did. "If you want to cut my emotion, then I go home and change my job," he said.
Having held out for 90 minutes in the goalless affair at Liverpool on Monday, United fell behind after just 30 seconds when a range-finder from Marcos Alonso found Pedro in space behind United's defence.
It set the scene for a woeful United defensive performance that angered Mourinho, who was forced to watch real excellence from the same Chelsea players who had failed to perform for him in the build up to his sacking last December.
"We made incredible defensive mistakes and you pay for that," said Mourinho, whose only previous Premier League experience of seeing his side leak in so many goals was when Chelsea were beaten 5-3 by Tottenham Hotspur in 2015.
"If we score a goal like we almost did for 2-1 the game would be different," added Mourinho, whose day was made worse by a serious knee ligament injury to defender Eric Bailly.
Wednesday's match should prove some managerial joust with Guardiola, who won their first Manchester derby, also sounding a mite desperate to get back on the winning trail again.
He knows how Mourinho feels, having gone back to Barcelona in midweek and suffered a similar 4-0 trouncing.
City had to come from behind after John Stones gifted Southampton the lead with a misplaced pass to Nathan Redmond.
The draw, secured by Kelechi Iheanacho's second-half equaliser, means City, who started life under Guardiola with 10 straight wins, have now not won for five games. It equals the Spaniard's worst run as a manager when he was at Barcelona.
"You can win 10 times and then you are not able to win five times. I have to discover the reason why and I am going to find that," Guardiola vowed.
(Reporting by Neil Robinson; Editing by Ian Chadband)
