Manchester United legend Paul Scholes believes Lisandro Martinez is already a key player at the club.
The Argentine centre-back has shown his quality under new boss Erik ten Hag, after signing from Ajax in the summer.
The defender, who was knocked for his height earlier in the campaign, was again immense as United bested Arsenal 3-1 at Old Trafford in the Premier League on Sunday.
United legend Scholes said: "At United it's about the determination more than anything.
"You know the talent is there but it's about getting up to people, stopping people, getting up to people, being solid at the back.
"Having that solid back four now is helping them. Martinez coming out of that might be a worry going forward."
Scholes added on the game: "I go back to possession where Mikel Arteta's saying he's in control of the game with his interview there. It doesn't matter.
"There are so many teams in these big games where they come away from Old Trafford a lot of times in big games wondering how have we not won, we've played great."