The Portuguese's position had come under question after slipping twice to defeat in the opening three fixtures of the 2018/19 season, while the United boss was accused of a multitude of sins, not least being unable to properly develop the players at his disposal.
One player about whom Mourinho cannot be charged with the latter crime, however, is striker Romelu Lukaku.
Signed from Everton at great expense in the summer of 2017, the Belgian top-scored for the Red Devils last term and has made demonstrable advances in several areas of his game, such as his link play, creativity and aptitude for playing in a target-man role.
This season, Lukaku has hit the ground running, continuing the fine form he showed with the other Red Devils, Belgium, at the World Cup by notching four times five Premier League appearances, averaging a goal every 95.6 minutes.
Despite a remarkable output of 105 Premier League goals at the age of 25 – many of which scored for West Bromwich Albion and Everton, clubs outside the division's established elite – Lukaku remains a notch or two below the game's very best strikers in the eyes of many.
That could all be about to change, though, thanks to a subtle but significant development the United No.9 has made in recent months.
Lukaku has often been criticised for the chances he misses. Already this season, clear opportunities squandered in the home defeat to Tottenham Hotspur and the away win over Burnley – in which he scored twice – have been used to pinpoint the striker's unreliability in front of goal.
While it is true that, taken in isolation, a player of Lukaku's ability should expect to do better with such scoring opportunities, it is also true that the increasing regularity with which the former Chelsea man is finding such chances is indicative of a striker entering the elite bracket.
Indeed, the old maxim that it is better for an out-of-form striker to be missing chances than not getting chances at all, while a tired cliché of sorts, has a strong element of truth: it is a better long-term strategy to accumulate a high volume of chances and score them at a steady, unspectacular rate than it is to rely upon an above-average conversion rate.
Take, for example, Harry Kane. The Tottenham striker is regarded by many to be the best No.9 in he world. In 2016/17, he converted chances at a rate of 26.4 per cent, returning 29 Premier League goals for the season.
Last term, his conversion rate plummeted to 16.3 per cent, yet he increased his shots output from 110 to 184. His reward? A first-ever 30-goal haul.
Generally speaking, above-average conversion rates will, at some point, regress to the mean; Kane had never produced a seasonal average above 20 per cent in his career before 2016/17, nor has he done so since; scoring at such a rate over a course of years is likely unsustainable.
What he and Tottenham have done since, though, is to further emphasise the England captain's ability to find dangerous pockets of space in and around the penalty area and get the ball to him in such zones with regularity; a similar approach has seen Cristiano Ronaldo remain so prolific over the last decade – it's all about volume.
Now, back to Lukaku. In his final season with Everton, he returned a career-high 25 league goals, and he did so from 110 shots, for a conversion rate of 22.7 per cent.
Last season, his first with United, Lukaku's conversion rate fell to 18.6 percent, while he also took fewer shots in total, resulting in 16 Premier League goals for his new club – a respectable return but hardly earth-shattering.
This term, however, Lukaku has upped both the frequency of his shooting and the general quality of the chances he is finding. While the fact his current strike rate is almost double what he averaged for last season is in part due to a hot-streak of finishing – regardless of the aforementioned high-profile misses – which has seen his conversion rate rise to 26.7 per cent over an admittedly small sample size, the underlying statistics tell a much more concrete tale.
Looking at Lukaku's average expected goals (xG) – the metric which uses historical data gauge chance quality – for the season, we see that, regardless of his finishing being way above his mean and therefore difficult to sustain, the chances he is getting are adding up to almost double the per-90-minute xG of last term – up at 0.88 from 0.49.
And while five games of a new season is far too small a sample size from which to judge Lukaku to have entered the pantheon of the world's finest strikers, this trend of increased xG actually dates back a little further, to around April of last season, as detailed in the above graphic from the Football Whispers Lab.
The reasons for this uptick are likely manifold. There is, of course, the need for Lukaku to be serviced with such chances, possibly a result of systematic tweaks by Mourinho aimed at freeing his creative players.
Most importantly, though, this trend signals a significant improvement in Lukaku's ability to get himself in front of goal with the ball at his feet, or on his head – or off his midriff, as was the case against Watford.
He will continue to miss chances – all strikers do, even the very best. But what is much more important, and what deserves to be valued much higher when assessing his place among the game's best forwards: Lukaku is now playing the numbers game as well as anyone around.