Dimitar Berbatov has explained the reason why Luke Shaw has been "transformed" at Manchester United this season.
Shaw, 25, is enjoying a fantastic campaign with the Red Devils and shone in Sunday's Manchester derby, scoring and keeping a clean sheet in a 2-0 win at the Etihad.
In previous seasons, the left-back has been plagued with injuries and lacked consistency as he struggled to live up to the £30million fee United paid Southampton in 2014.
This prompted Old Trafford chiefs to sign Alex Telles from Porto last summer and the Brazilian was expected to share minutes on the left of the defence.
But Shaw has nailed down the starting role in recent months and Berbatov claims he has been spurred on by increased competition at left-back.
"I thought Luke was man of the match [against City]," the former United striker told Betfair . "He was great in that game. He was going into tackles, working hard, passing well and playing in a no-nonsense manner.
"His transformation under Ole shows that he has grown into the position.
"I saw a meme saying that since United signed Alex Telles, Shaw has turned into the best defender in Europe. If we put the joke aside, this is what competition can do for you sometimes.
"You feel comfortable, then the team buy someone in your position and you realise that you need to prove how good you are. This then brings the best out of you.
"Competition is certainly one of the factors that has helped him develop and improve. It also comes down to personal motivation, you don't know about his private life and whether he feels comfortable. He was great on Sunday, as was the whole team."
Berbatov has been so impressed by Shaw that he insists he is a better option at left-back for England than the likes of Chelsea's Ben Chilwell or West Ham's Aaron Cresswell.
Is Luke Shaw England's best left-back? Have your say in the comments.
The Bulgarian added: "There are lots of good players in both the left and right-back positions for England. Gareth Southgate has decisions to make and he is now the best left-back in my opinion.
"He now just needs to back it up. He just needs to stick to his trends, keep it simple and he'll be an even better player.
"England have some great talent right now and hopefully Gareth can fit it all together and made a great team out of it."
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