The trio were at a coaches forum in Nyon, France, during transfer deadline day.
While Arsene Wenger was exchanging pleasantries with Bernabeu legend Zidane, Jose Mourinho walked past but seemed unable to get a word in.
The Gunners and Red Devils bosses have a fierce rivalry, dating back to when the latter first arrived in the Premier League.
While in charge of Chelsea, the Portuguese accused his north London counterpart of being a ‘voyeur’, and tussled with him on the touchline during a particularly feisty match.
Even since being appointed to his new role at Old Trafford, Mourinho has appeared to take a pop at Wenger when annoyed by the 66-year-old speaking about Paul Pogba’s high price.
It will be a few months before the pair have to face each other again, with United facing Arsenal at home on November 19.
Sure to be a hotly-contested affair with both teams going for the top-flight title, it wouldn’t be a major surprise if tempers flared between the duo yet again when the clash comes in to view.
However, Mourinho will likely be quietly confident going in to it, having never lost to the Frenchman in a competitive match.