The European champions were drawn alongside Spurs, Borussia Dortmund and APOEL in Group H, but will have to wait until next month for their meeting with the Premier League side.
The Spaniard has scored three goals in his first four Premier League games, all with his head, including in the 2-1 victory over Leicester on Saturday.
Mourinho and Guardiola are both bidding to win the Champions League for a third time, with Man Utd and Man City both priced at 11/1 in the betting, ahead of Antonio Conte's Chelsea (18/1), Klopp's Liverpool (22/1), and Mauricio Pochettino's Tottenham (40/1).
Barca president Josep Maria Bartomeu has claimed the Catalans will have a "more competitive" side this season than last despite losing Neymar after splashing out a fee that could rise to 145 million euros on 20-year-old French winger Ousmane Dembele to replace the Brazilian. In his first one and a half, he's won two Champions League trophies and one La Liga title. And, with a quintet of EPL teams now in the reckoning, it could once again be England's chance to shine on Europe's biggest club stage. The one-time Europa League winners best Champions League campaign came in the 2010-11 season when they reached the Quarter Final, but were beaten by eventual winners Barcelona.
Spain worldwide Marco Asensio is considered to be one of the brightest stars in European football, and was linked with a move away from the Santiago Bernabeu in the past month.
While you're here.Watch Eamon Dunphy, Andy Reid, Dion Fanning and Wooly on a SportsJOE Live Irish football special.
Ten years ago, a new era dawned in the Champions League.
Can Real Madrid make it a three-peat? Firstly, Feyenoord, who have started the new season well since last season's heroics, will host Manchester City, who's minimum expectations will be to progress through the group.
Asensio said the Frenchman had compared him to Barcelona maestro Messi, who is arguably the best player in the world.
'Now, in the Champions League, we could play Bayern Munich, Real Madrid or Barcelona - those teams who all won the trophy many times.