Phil Neville believes Juan Mata is becoming one of Manchester United's most important players under Jose Mourinho.
The Spaniard scored the winner as United beat rivals Manchester City 1-0 at Old Trafford on Wednesday to progress to the EFL Cup quarter-finals.
Neville was a first-team coach under David Moyes when United signed Mata from Chelsea, then managed by Mourinho, in January 2014 for £37.1m.
Neville admitted he expected the Portuguese boss to sell Mata when he took charge at Old Trafford last summer but the former Blues attacker has chipped in with a number of key contributions this season, scoring three goals in six Premier League and EFL Cup starts.
"I was here [at Manchester 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."
Sky Sports football expert Jamie Carragher agreed with Neville's analysis, praising Mata's goalscoring instincts.
"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, counter-attacking and flying wingers. He's a number 10, what number 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 number 10s at other teams and say he's neat and tidy but he doesn't score? He gets goals."
Speaking to Sky Sports after the victory over City, Mata admitted it was crucial to bounce back from United's 4-0 Premier League defeat to Chelsea last Sunday.
"After the defeat we had in London, it was a massive game for us," Mata said.
"It was a derby and it is always very difficult to play against Man City, they play very good football and I think we gave 100 per cent and we won."
And on his match-winning goal, he added: "Every time you score an important goal it is a great feeling but the most important thing was we fought together and I think we left everything on the pitch."