Ander Herrera believes Manchester United team-mate Paul Pogba is capable of becoming the world's best player.
The France international scored a late headed winner as United came from behind to beat Middlesbrough 2-1 at Old Trafford on Saturday.
That was a second goal in December for Pogba, who re-joined the club in a world-record transfer from Juventus last August.
Jose Mourinho's side have now won six straight matches across all competitions and while Herrera feels his midfield colleague has been influential, he is also excited by what is still to come.
"Pogba is a midfielder who has all the qualities," Herrera said to Sky Sports.
"When you are a midfielder you normally have some special qualities but he has everything.
"He can shoot, head and defend and he can dribble one-v-one, but he's still 23.
"He's now in a very good moment but we can be optimistic with him because he can be even better.
"He can be one of the best in the world and he wants to do it. He wants to be it."
Herrera also praised two of United's other new additions this season – veteran striker Zlatan Ibrahimovic and playmaker Henrikh Mkhitaryan – as the club prepare for Monday's away Premier League game against West Ham.
He continued: "The thing that I like most about Zlatan is he is not happy enough.
"That means how ambitious he is. How much he wants to achieve for this club. He's 35 and still training like a kid every day.
"The fans and the club and the staff have been patient with [Mkhitaryan], that's what I like with this club.
"They knew how good he is but football is not always the case that in your first season you will perform at your best. You have to settle down in one place, adapt yourself to a new life and club, to a new role.
"Now we are seeing the best Mkhitaryan. Or almost the best, because I think he can be even better."
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