Manchester United's improvement this season has been significant, there's no doubt about that.

Erik ten Hag has not only made them more disciplined, but something resembling a team identity is beginning to take shape.

The Dutchman's signings have largely been effective as well. The jury is out on Antony, though he has shown a bit more promise lately. Otherwise, however, Ten Hag gets high marks in this area.

Casemiro and Christian Eriksen have, of course, been the standout individuals in this respect. The experienced pair have brought know-how, control and general quality to the engine room, with the Brazilian also providing the destructive tendencies they long lacked.

But their excellence also highlights the significant gulf in quality to their back-ups.

United look likely to have another busy pre-season in the transfer market, but if there's one area they still need to bolster, strangely enough it's where they're arguably strongest.

A step in the right direction

That midfield trio of Casemiro, Eriksen and Bruno Fernandes is among the best of its kind in the Premier League.

While the two new arrivals have made a real impact already, quickly becoming hugely influential, that's taken some of the burden off Fernandes, who in turn has flourished.

But when you take Casemiro or Eriksen – or both, as was the case against Leeds on Wednesday and when the two tussle again on Sunday – United simply don't have the same standard or type of player.

Obviously, you can't expect a team to have two world-class options for every single position, but at Old Trafford there has to be an acceptance that they need to get as close to such depth as possible if they are to be a long-term challenger to Manchester City under Ten Hag.

Marcel Sabitzer looked fairly assured and generally promising on his first start as he filled in for Eriksen, who is out until May, during Wednesday's 2-2 draw at home to Leeds United, but Casemiro's suspension saw Fred deputise.

Fred routinely proved before this season that he isn't equipped to play as a six, so him lining up in his compatriot's position may have caused fans some stress.

In fairness to him, he didn't really fill that role at all – but then neither did anyone else. He and Sabitzer both occupied very similar positions, so United were essentially playing with two eights rather than an eight and a six.

It's no wonder they often looked outnumbered when Leeds attacked. Not only was Casemiro absent, they didn't really have anyone occupying his void.

United cannot stand still

Fred's effort certainly can't be faulted. If there's one thing he stands out for, it's his work ethic.

He ran further than any of his team-mates on Wednesday, while only Luke Ayling (24) and Alejandro Garnacho (20) engaged in more duels than his 17.

Additionally, there were nine players to register 10 or more duel involvements, and only Ayling (66.7 per cent) had a better success rate than Fred (58.8 per cent).

But it's all well and good running around lots. He didn't actually offer a great deal of defensive protection, attempting just two tackles and making one interception.

Of course, you'd not necessarily expect those figures to be through the roof in a game United largely dominated, and any lack of protection would've been forgiven had he been an effective user of the ball.

He wasn't.

The only United player (minimum 10 pass attempts) with a poorer completion rate than Fred (62.5 per cent) was Garnacho (61.9 per cent).

It was a frantic game, so it's not like being a world-class playmaker is something a player can just switch on and off.

But when United were chasing a winner, their passing seemed to get even sloppier. Fred in particular was guilty of coughing up possession in his own half on several occasions when Ten Hag's men threatened to spring a counter or a direct build-up.

Fred certainly has his uses, and Ten Hag has shown that by frequently introducing him from the bench in the second half of matches to inject a bit of energy.

But Wednesday was another reminder of how he really needs a number six behind him rather than to be the player – or one of – expected to provide control as he's like a deer in headlights against teams who press high. In a number eight role with freedom to attack, he could be a reliable option as he's technically better than many give him credit for – he cannot be the one to provide the balance, however, because he just doesn't have the composure.

United took a big step last year by finally addressing the midfield needs that had dogged them ever since Alex Ferguson retired in 2013.

Yet, if they are to push on from what will likely be reflected on as a positive debut campaign for Ten Hag, United cannot stand still. The signings of Casemiro and Eriksen need to be the start.