The Portuguese has always been known for grinding out results against his closest rivals – but since taking charge at Old Trafford the Red Devils have often come up short in crunch fixtures.
United have faced Manchester City, Liverpool, Chelsea, Tottenham and Arsenal a combined total of 24 times since Mourinho's appointment in 2016.
His team have won just eight of those matches, losing nine and drawing the other seven – amassing 31 points from 24 games.
That is a worse head-to-head record than all the other sides in that mini league except for Arsenal, who have just 20 points from 25 matches.
Manchester City top the table with an impressive 44 points from 25 games but Liverpool have lost three fewer than their main rivals for this year's title with Jurgen Klopp's men only losing four times to the 'big six' since 2016.
United left Anfield last season with a 0-0 draw as they took a defensive approach against a Liverpool side who, at the time, were out of form.
Mourinho's men had just one shot on target last October and that lack of goal threat from United has been apparent against their key rivals since the former Chelsea manager took over.
They have had just 263 shots in the 24 previous meetings against City, Liverpool, Chelsea, Spurs and Arsenal – 51 fewer than the Gunners, who are next on the list.
But it is not a case of keeping things tight at the back either, with United facing 102 more shots on their own goal than Liverpool have in the same group of fixtures.