The defender made headlines during the international break, scoring the Republic of Ireland's stoppage-time equaliser in their 1-1 draw with world champions Germany earlier this week.
The Black Cats manager told Sky Sports News: "It's the whole thing, definitely the influence of Manchester United because he was there playing with top players, and I am sure he took things from different characters. He cannot imitate, he cannot be his previous captain, Roy Keane, but he can imitate other ones. It's just to learn and put what you are into the job.
"He does it naturally, I can tell you, there are no issues. He's always there, he's always on time, he is always fit, or most of the time, he looks after himself, he represents the club well, the players. That's why he is the captain.
"You have different types of captain at different clubs, sometimes because of how good they are and they have to be the captain, sometimes because they lead by example, sometimes because they have even better, the package he's got, he represents us on the pitch."
Sunderland sit 13th in the Premier League table after recording their first win of the season last time out.