The Portuguese, now in his second spell at Stamford Bridge, is a firm fans' favourite in west London, despite having been unable to secure the European crown he won at Porto and Inter Milan.
It is a competition the Blues look well placed to challenge for this season, with progress to the knock-out stages guaranteed should they win at Schalke on Tuesday - a club managed by a familiar face.
Di Matteo oversaw Chelsea's miraculous Champions League triumph in 2012 and, having last month taken his first job since his Stamford Bridge sacking, now stands in the way of his former club as they attempt to secure top spot in Group G.
Like Mourinho, the Italian will go down in Chelsea folklore but the current incumbent is not interested in any talk of an individual battle on Tuesday.
"I don't play against him," the Portuguese said of the Schalke boss, who also shone for Chelsea as a player.
"If I play against him, he wins because he plays better than me.
"Unless I am fitter, which I don't know, but normally he wins because he is much better than me.
"It is Chelsea against Schalke, it is not me against Di Matteo."
Mourinho appeared reluctant to talk about the Italian, yet was more forthcoming when it came to the importance of winning in Germany.
Chelsea head into the match three points clear at the top of Group G, yet it has been a topsy-turvy campaign having drawn at home to Schalke and away at Maribor last time out.
"The group is easy to analyse," Mourinho said
"Any one of us can finish first, second or third.
"Obviously Sporting (Lisbon) and Maribor can finish fourth also, but we can finish first, second or third.
"To finish third and go to the Europa League should be something that would be against the evolution of this team.
"This team wants to be a very good team and to be a very good team you have to play against the best teams in the best competitions.
"I would feel very frustrated if we have to go to the Europa League, so the objective is to get enough points in these two matches to go to the last 16."
Chelsea travel to Gelsenkirchen with just one new injury concern after Petr Cech injured his back warming up ahead of Saturday's Premier League home match with West Brom.
The Czech Republic international was okay to fulfil his watching brief against Albion, against whom the Blues won a 14th match of the campaign in all competitions.
Diego Costa and Eden Hazard goals secured a win far more comfortable than the 2-0 scoreline suggests, with the Baggies forced into damage limitation mode following Claudio Yacob's red card just before the half-hour mark.
Mourinho was impressed by the manner in which West Brom held firm, so too was their manager Alan Irvine.
"There's been an 8-0 in the Premier League this season and when you're 2-0 down and down to 10 men with an hour to play at Stamford Bridge then you obviously fear the worst," the Baggies boss said.
"What I spoke to the players about at half-time was making sure that we were together as a team all the way through, regardless of what happened.
"They felt aggrieved at half-time by a couple of things that had happened and it was important to get them focused and make sure that we didn't end up on the wrong end of a high score
They deserve credit, as Jose said."
Source : PA