Zlatan Ibrahimovic preserved our unbeaten run but the 1-1 draw with Everton was an eighth home stalemate of the season.
The Reds were staring at a first defeat since the 4-0 at Chelsea in October before Zlatan's calmly taken penalty sent Robles the wrong way and salvaged a point.
In many of the other seven Old Trafford draws, United have played well and been thwarted by a combination of deep defences, inspired opposition goalkeepers and the pressure of expectations.
The biggest frustration is that we don't seem far away, we are unbeaten in 20 games in the league stretching back to October.
Mourinho has won one trophy already and can still take us into the Champions League by winning another - if that happens (as it should), then his first season must be considered a success.
Despite what the critics will say, there has been definite improvement but the problem is clear: United do not score enough goals and look at least one striker short.
Zlatan has enjoyed a hugely productive first season in English football and his late goal on Tuesday took him to 27 for the season.
However, he has had his fair share of missed chances, Marcus Rashford is lacking confidence and Anthony Martial has failed to secure a regular starting place.
One on the main differences between this side and that of Louis van Gaal has been the more eye-catching style of play, with a preference for fluid build up and getting the ball into the box quickly.
The performance against Everton, however, was one of the worst this season and a throwback to the days of Jose's immediate predecessor.
Perhaps because of the absence of the injured Juan Mata, United struggled for creativity with much of the play in front of the Everton defence - often sideways and backwards without showing any real strategy to break down the visitors.
On a night when we lacked cohesion and incisiveness a reshuffle to the side saw Herrera drop to left-back following the withdrawal of Daley Blind at half-time.
Despite the presence of Matteo Darmian and Luke Shaw on the bench, Herrera swapped position with Ashley Young to move to right-back.
Shaw did eventually come on, and would have a hand (literally) in the equaliser, but only as an enforced change after Young's injury.
It was all very confusing and muddled and that transcended through the team on a rare off-night for the Reds.