Forget the rugby, the biggest collision this week will come not at Twickenham, but Stamford Bridge on Saturday lunchtime, when Chelsea and Arsenal go head to head in the Premier League.
With the Blues, tipped by most experts to defend their title, languishing in 17th place with four points from five games, and Arsenal smarting from a damaging defeat in Europe on Wednesday, this is a big game for both sides. The victors will gain significant momentum, while the losers will be floored, possibly for the season.
At the start of the week it looked as though Arsene Wenger had his foot on Mourinho's throat in a dramatic reversal of footballing fortunes.
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Before winning the Community Shield in August, Wenger had never got the better of a Mourinho team - but the monkey is off Arsenal's back and second straight win over the Blues on Saturday could consign them to the relegation zone and could leave Mourinho mortally wounded.
However, the chances of the Portuguese losing back-to-back home league games for the first time in his career appear to be receding thanks to events in Europe.
Chelsea rediscovered their mojo as they beat Maccabi Tel Aviv 4-0 on Wednesday, while Arsenal blotted their copybook in spectacular fashion, losing 2-1 to minnows Dinamo Zagreb in Croatia.
It does not bode well for the Gunners, whose forwards have managed only two league goals so far this season.
It's no secret that Wenger and Mourinho do not get on. They did not shake hands at the Community Shield, they almost came to blows on the touchline last season and Mourinho famously described Wenger as a "specialist in failure".
Wenger has been at pains not to fuel the fire, but it hasn't worked, says Amy Lawrence of The Guardian. "The history of mutual antipathy runs deep, and when Wenger said he did not wish to comment on whether he would shake the Chelsea manager's hand, his expression tightening, the tension this whole brouhaha provokes was palpable."
Aside from the managerial rivalry there are plenty of other subplots, as Gunners goalkeeper Petr Cech returns to his old stamping ground and Chelsea midfielder Cesc Fabregas comes up against his former club once again.
There are also question marks over the participation of some big names. Arsenal defender Per Mertesacker is fit, but may struggle to force Gabriel Paulista out of the team, while Chelsea skipper John Terry was not missed in midweek.
Dropping Terry would be a huge statement from Mourinho, but he may be inclined to be bold given his situation.
The Blues will also be without Willian and Pedro, although Radamel Falcao could feature for the home side. The team Mourinho picks will be fascinating.
The decline of Chelsea's spine has been alarming, says Alistair Tweedale of the Daily Telegraph. Terry "already has a worse disciplinary record than he did in playing every minute last season", he notes. Nemanja Matic has been "rash" and is "no longer the immovable barrier in front of Terry and co".
Eden Hazard's work rate has dropped dramatically and Diego Costa, whose goal per shot ratio has more than doubled this season. Finally there is Fabregas who "has probably been the most underwhelming of the lot".
But Saturday's game could have come at the right time. "The Champions League provided some respite but perhaps a home tie against his favourite worst enemy Arsene Wenger is the perfect remedy," says Tweedale.
The match is not a must-win for the two sides, but more of a must-not-lose, and that is the kind of situation that favours Mourinho.
"A win, no matter how they get it, would give the defending champions a shot in the arm and deflect the pressure from Mourinho on to Wenger," says Martin Keown of the BBC. "Wenger is already getting some stick and that will intensify if Arsenal lose."
