Paul Scholes has a theory on why Luke Shaw hasn’t been playing for Manchester United

"A couple of years ago, I thought we were signing the best left-back in the world."

Luke Shaw made his first start for Manchester United since April in their Champions League tie against CSKA Moscow at Old Trafford on Tuesday night, and the left-back impressed in a rare outing for Jose Mourinho's side. The 22-year-old put in the type of performance United fans had expected to see when he joined the club from Southampton for £30m in 2014. He was a constant threat down the left-hand side and excelled in the wing-back role, as the home side claimed a 2-1 victory. https://twitter.com/OptaJoe/status/938146755606204416 Before the game kicked-off, Paul Scholes, Rio Ferdinand and Steven Gerrard questioned Shaw's professionalism and asked why a player of such obvious talent has not been used more often by Mourinho. The former England trio effectively pinned the blame for Shaw's absence from the first-team on the player himself, and asked why he hasn't rose to the challenge set by his manager. Scholes questioned Shaw the most, and suggested that the 22-year-old has not been in Mourinho's plans because he hasn't been living a "clean" life. https://twitter.com/SportsJOE_UK/status/938160316743118848 "It's difficult to say as we don't see what goes on behind the scenes, (but) I don't think he lives his life as clean as he possibly should do," Scholes said on BT Sports' coverage of the Champions League, before comparing the left-back's physique to that of Wayne Rooney.

"With his body shape, he looks like a player who needs to be playing every week. We had Wayne Rooney, who was a player if he missed a couple of games you knew, he wasn't looking after himself. He needed to be playing all the time, Saturday, Tuesday, whatever it may be. With Luke Shaw, is he going to get a run of 10 games in the team? I'm not sure, the problem he has got is that Ashley Young has been brilliant at left wing back. I hope there is a future for him. A couple of years ago, I thought we were signing the best left back in the world. But if you can get him playing there's a chance."

You can watch Scholes, Ferdinand and Gerrard here: https://twitter.com/btsportfootball/status/938126551253622784 Shaw has struggled for form and fitness at United, and almost had his career ended after suffering a horrific double-leg break in 2015. Since returning to action, he has had his professionalism questioned by Mourinho, and many expect him to leave the club in not too-distant future, possibly as part of a swap deal with Tottenham's Danny Rose. Yet, Shaw showed on Tuesday night that it would be foolish to write him off just yet, and he could still become an excellent player.