Chelsea face a key meeting with London rivals Arsenal on Sunday, knowing that a win will go a long way to emphasising their title favourite credentials, while anything but will surely insert an until now hidden element of doubt when it comes to the Stamford Bridge outfit.
Manchester City have started slowly in their defence of last season's title, but are now beginning to move into a decent patch of form, and would be delighted to see Yaya Toure net his first goal of the season away to Aston Villa. If they can get the Ivorian up to anything like last season's form they will undoubtedly be Chelsea's biggest rivals.
But it isn't just the Sky Blues that Mourinho's side would be at risk from were they to fail win this weekend.
Though Liverpool and Manchester United are showing patchy results, Arsene Wenger's team are coming into some good form themselves. An encouraging result at a side that beat them so comprehensively last season would give the Gunners even greater confidence to gatecrash what many have predicted would be a two-horse race between Chelsea and City this season.
With Danny Welbeck starring against Galatasaray in midweek, and Arsene Wenger seeming to have stumbled onto a system of utilising both Mesut Ozil and Alexis Sanchez, the last thing Mourinho would want is to have to deal with another Premier League contender.
Last season saw Chelsea fall short and end up in third place while Pellegrini's City and Liverpool blitzed most sides before them on the way to a tight finish. But plenty of pundits and fans feel the title was Chelsea's to lose last season, with tight defeats to the likes of Aston Villa and Crystal Palace throwing spanners in what seemed like a determined assault on silverware.
In those games it was a lack of a bonafide goalscoring centre forward, that could would work well within the existing Blues side, that cost them. But in Diego Costa, Chelsea have a forward that has so far seemed unplayable in his six Premier League games, and that is with Mourinho stating the former Atletico star is carrying an injury.
The Portuguese tactician, and all associated with the Stamford Bridge club will be eager to keep the veil of untouchability about Costa for as long as possible, not to mention the effect that it has on the side themselves, still yet to taste defeat in the league.
But dropping points at home to Arsenal, even an Arsenal seemingly improved from last year's 4th place finish, may just show that this Chelsea side won't have everything their own way this season.
And getting his side to ride a wave of confidence and impressive performances, all the way to May or as close as possible, is something Mourinho wants very much indeed.