Never did the vast majority of Manchester United fans envision there being a day when Marouane Fellaini’s return from injury would be regarded as a major boost to their side’s fortunes. But that was exactly the case when the Red Devils hosted Crystal Palace at the weekend.

The Belgian midfielder, who was subjected to boos by sections of the Old Trafford support at times last season, scored twice against Roy Hodgson’s goalless and pointless side, helping United close the goal difference gap to Manchester City at the top of the Premier League with a 4-0 win.

Aside from his two goals, both from close range, doubling his tally for the season so far, Fellaini’s work against the Eagles was largely excellent. He completed 90.4 per cent of his 52 passes, made one key pass and completed one dribble. Defensively, he made four tackles, two interceptions and one clearance.

The quality of opposition was low, but it was a stellar display from Fellaini, and evidence of the 29-year-old’s vast improvement under José Mourinho.

Initially to the chagrin of many United fans, Mourinho has always been a staunch supporter of Fellaini, even when the former Everton man’s lumbering cameo against his former team at Goodison Park last season resulted in a clumsily conceded penalty and two points dropped.

That moment seemed to mark the nadir of the towering midfielder’s unlikely United career, with the ill will from many sections of the fan base apparently pointing Fellaini in direction of the Old Trafford exit door.

Rumours of a move to Turkey surfaced in the summer, given weight by the fact that the player is still to commit to a new contract with the Red Devils, his current deal expiring at the end of the 2017/18 campaign.

But Mourinho insisted that Fellaini remained key to his plans, even in light of Nemanja Matić’s signing from Chelsea, and that Galatasaray had more chance of signing the Portuguese tactician himself than the Belgian midfielder.

To many, Fellaini is seen as the last relic of the forgettable and regrettable David Moyes era. The Scottish manager’s unsuitability for the Old Trafford hot seat was in evidence in his first transfer window, dithering over major targets before launching desperate late bids for familiar faces Leighton Baines and Fellaini, with a 50 per cent success rate.

Never truly embraced as a “United player”, the Belgian’s style – all aerial prowess and elbows, and lacking in speed of feet and thought – grated with many. And few still would argue that the team should be built around the bustling Brussels native, or that he should remain in the side at the expense of Matić or Paul Pogba once the £89million man has returned to fitness.

But his work to improve his game, technically and from a perspective of temperament and leadership, deserves to be recognised and commended.

For example, not since his very first season at Old Trafford in 2013/14 (88.5 per cent), has he produced such consistently high figures for pass completion as under Mourinho (86.5 per cent last term and 85.2 this).

Remarkably, Fellaini is now making more passes per 90 minutes that at any point during Louis van Gaal’s reign, when possession and slow, meticulous circulation of the ball was the order of the day. He’s also winning fewer headers, which suggests he is becoming more comfortable with the ball at his feet, and his team-mates trust him on the ground more than before, rather than aiming high to the Belgian at every opportunity.

Fellaini’s goals contribution this season – currently set at 0.9 per 90 minutes – is very unlikely to be sustainable given that he is scoring at the rate of an elite striker, but it again points to a new-found confidence. It took him a while to get there, but he now times his entries into the penalty area to to perfection, and finishes confidently with head or foot.

His first goal against Palace at the weekend was a prime example of this. As United methodically worked the ball wide to Ashley Young on the left, Fellaini sauntered into the box, calmly side-footing the former England international’s cross into the net from close range when it arrived at the back post.

With Fellaini, it seems confidence has always been the key. Having been told for so long that he didn’t belong at Old Trafford, that his style was anathema to that espoused by the 20-time champions, he appeared to doubt himself. An identity crisis set in and it took the man management of Mourinho to correct it.

Not always known for the arm-around-the-shoulder approach, Mourinho saw in Fellaini a player who had taken to heart what he was being told about himself. By reassuring him and reasserting, over and again, that he belongs where he is and is a valued member of the squad, Fellaini is beginning to believe.