Former Manchester United defender Phil Neville believes Juan Mata is becoming a crucial player for Jose Mourinho.
Mata, 28, scored the only goal of the game as United beat Manchester City 1-0 in the EFL Cup fourth round at Old Trafford on Wednesday.
The Spain international arrived at United from Chelsea -- then managed by Mourinho -- in 2014, with Neville first-team coach at Old Trafford at the time.
"I was here [at United] when we actually bought Juan Mata," Neville told Sky Sports. "He is never injured, he provides a lot of assists, he plays in two or three different positions, and he scores important goals.
"I actually thought he would be the first out of the door when Jose came, but he's actually becoming one of the most important players."
Ex-Liverpool defender Jamie Carragher echoed Neville's comments and also believes Mata is a vital player for Mourinho.
"He has played 116 games [for United]," Carragher said. "We looked at the stats, he has been involved in nearly 50 goals. He has scored 29 and assisted 18.
"Sometimes I think he gets criticised because Man United are used to pace, counterattacking and flying wingers. He's a No. 10, what No. 10 does have pace? There's very few.
"As Phil said, he is never injured but he gets goals and assists. He delivers. How many times do we talk about No. 10s at other teams and say he's neat and tidy but he doesn't score? He gets goals."