It had started to become clear last week but Pep Guardiola is willing to use a back-three more often this season, now that he is bedding in at Manchester City.
Unlike Chelsea, who have a different philosophy of play, it hasn't led to a positive change in results yet.
And beyond the fact that Guardiola's prizes possession more than Chelsea's Antonio Conte, their use of a 3-4-3 formation differs in its application.
In Chelsea's recent upturn in form, Conte has used Victor Moses and Marcos Alonso as the wide players in the formation.
Moses has traditionally been a winger whereas Alonso has been accustomed to playing at left-back. The latter's inclusion means, for example, that Chelsea's biggest danger man Eden Hazard on the left of the forward three can play further up the field as Pat Nevin pointed out on Newstalk.
"If you're Eden Hazard playing the 3-4-3 and you've got somebody behind you like Alonso in the left-back/left-midfield area, you're starting the game 20 yards further up the park. What a difference it's made to him and Pedro," said the ex-Chelsea and Everton winger.
Moses too has knuckled down to become Chelsea's outlet along the right flank.
If you watched Match of the Day on Sunday night, pundits Phil Neville and Jermaine Jenas were showing presenter Mark Chapman and viewers what went wrong as City defender John Stones gave the ball away for Southampton's opening goal.
ChelseaÂ’ manager Antonio Conte gestures during the English Premier League soccer match between Chelsea and Manchester United at Stamford Bridge stadium in London, Sunday, Oct. 23, 2016.(AP Photo/Kirsty Wigglesworth)
Whereas, Stones went for a sloppy pass back to Vincent Kompany which eventually led to Nathan Redmond being played in, the other available passing outlet was Leroy Sane out wide.
But as the pundits pointed out, the young German, who was close to the half-way line, needed to be a little further back to receive possession from Stones.
But Sane is an advanced player rather than the type of wide-man that could do the type of job that Alonso and Moses are doing for Chelsea.
Like Raheem Sterling on the other side, they are more naturally wingers or more reliably in Sane's case, inside-forwards that prefer playing further up the pitch.
So dropping back so deep would not necessarily be natural for either player.
In contrast, the type of players Guardiola previously worked with at Bayern Munich and Barcelona would be more suited to the wide roles in a 3-4-3 shape in the type of scenario that saw Stones give the ball away.
David Alaba, Dani Alves, Philippe Lahm and Juan Bernat are the sort of players who can transcend the role of full-back and wide midfielder and fit more snugly into a hybrid role on the flank.
In contrast, Guardiola currently has to work with full-backs like Bacary Sagna, Pablo Zabaleta and Gael Clichy who are not quite as flexible as the aforementioned quartet - none of the three started against Southampton in any case.
Long-term though, that will likely be an area of the pitch Guardiola will look to address in the transfer market.
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