Although he is now firmly established as the Reds’ first-choice stopper, De Gea had to deal with considerable scrutiny after Sir Alex Ferguson signed him from Atletico Madrid in the summer of 2011.
Carroll himself came to Old Trafford a decade earlier and although he's now with Olympiacos, the club’s next Champions League opponents, the Northern Ireland international still takes a keen interest in matters at United.
De Gea's displays as the last line of defence have helped United keep three consecutive clean sheets in a three-game winning streak, and speaking to MUTV, Carroll said: "Sir Alex stood by De Gea, he's gained more experience and he’s now more relaxed playing in the Premier League.
“You can see it in games - he’s a great shot-stopper and he’s coming for more crosses. Sir Alex believed in him, and he’s proved that he is worth the money that Manchester United paid for him.”