The 21-year-old, who started the season at right-back, was thrust into the Spurs XI for the first time in over a month in his preferred centre-half position.
And he impressed with a series of timely challenges against Steven Fletcher and debutant Jermain Defoe.
Pochettino said: "I am very happy with Eric, and with his performance. I think he can play like a centre-back and like a full-back.
Eric Dier has been a stalwart for England Under-21s
"It was a very difficult game. To play against two strikers like Fletcher and Defoe, and then Connor Wickham, was a real challenge and his performance was very good."
Dier later told TottenhamHotspur.com: "I’m really happy to get the three points.
"It was a tough game, Sunderland played five at the back, they sat back and made it really hard for us, so it was great to get the win in the end."
The former Sporting Lisbon player was grateful to have a player of Belgium international Jan Vertonghen alongside him.
"I really enjoy playing and to get the chance to play next to Jan – I learn a lot from people like him in every game and every training session because he’s a great player," he added.
"He’s obviously been here for a while and done really well, so it’s great to team up with him."
