Well firstly i think he's a great right back, who will be here long term so therefore we have a player who will be in the starting lineup whenever available.
Secondly, He has the winning mentality and fight that was the trademark of the Ferguson era, having played with the likes of rio, vidic, giggs, scholes, van der sar etc he knows the deal.
He's someone who wont back down when the game gets fired up, who can put a tackle in on someone to get the fans riled up in a derby, or as a bit of payback for a teammate getting clattered earlier, the little things that impact the mentality of the squad in tense situations. He's got a bit of Keane about him.
the only question mark is his fitness right now, but at 24, he wouldn't hypothetically take over from Rooney for years, and who says he wont get over his injury niggles by then. its all guess work and opinions, i just think he's a leader.