It's so hard to judge, unless you are seeing the player train regularly I suppose.
There are so many players we have got excited about watching U18 and Reserve team football.
Mats Daelhi
Joe Rothwell
Sean Goss
Larnell Cole
Tom Thorpe
Ravel Morrison
Josh King
Frederico Macheda
James Wilson
Adnan Januzaj
It's easy to discount these players since they've not made it at United, but the excitement and appreciation of their talent was pretty widespread.
The last of those 3 got opportunities, and it couldn't have started better for them. Goals on their debut, promising comments from fans and commentators alike, all with impressive performances and records at Reserve Team level. James Wilson was a ridiculously natural finisher, quick, could pick a great run in behind and take players on.
Everyone said Ravel had the talent, I watched a fair bit of him and am inclined to agree, but has never once showed that in senior football.
Tom Thorpe was a hugely highly regarded CB, Mr Reliable at Reserve Team level and arguably deserved a chance at first team level...especially when we were playing Carrick at CB. It never came and, again, after leaving United has struggled to find his level since in first team football.
Rothwell and Goss earned great praise for assured, calm performances built on really solid passing ability...again their opportunities never came....Rothwell is creating a decent career for himself at Championship level so far, last I saw of Goss he struggled at Rangers, and was back in Scotland first division on loan from Shrewbury.
Daelhi impressed massively time after time when I watched him in U18 level. He had a bit of everything, goals, created numerous chances, could pop up anywhere across that line between oppo midfield and defence, just had that knack for finding space. He was sold to Cardiff with Eikrem when Ole took the job. Similarly, Cole went to Fulham along with Tunnicliffe when Rene Mulensteen got the Fulham job. Tunnicliffe earned high praise, along with Ben Pearson from folks on here....though I personally didn't see United first team in them....but both Tunnicliffe and particularly Pearson are having good careers in the Championship, just read Larnell Cole is playing at FC United.
I guess the quite long winded point I'm making is you just never can tell how a given player's talent will translate on the bigger stage, at a higher level and under greater scrutiny and expectation.
Darren Fletcher was widely regarded as one of the biggest midfield talents in the U18 and Reserves, he was mentioned frequently. It took him years to develop into that mould at first team level.
He got stick from fans and media alike, at best writing him off as several levels below United grade, and at worst Fergies illegitimate love child.
Jesus, after the abuse I've seen the likes of Rashford get on here after a couple of bad games on the trot, I can only imagine there would have been calls for Fletch to be sold for 2 bob to Macclesfield.
Scott McTominay I'd never have pegged to be one of those that would start regularly for United. But, he's improved no end over the course of the last year, and though I accept we should be looking at additional talent in midfield, if he continues he should have a thoroughly decent United career.
I think it's particularly difficult for young players in central midfield, the level of positional responsibility and finding the balance between cobtributing to attacking play whilst not leaving your defence exposed for example? Maybe that's over stating it but, I don't know.