The on-loan Manchester City defender has been an ever-present for the Black Cats in the Premier League this season but for being ineligible for the home win against his parent club.
The versatile 23-year-old, who has been deployed at right-back by Sunderland boss Steve Bruce, made only 10 league appearances for City last season.
And although Onuoha has been a regular since joining the Wearsiders on a season-long move, he knows he must stay on his toes.
"It's been good to play in every league game I've been available for," he told the Sunderland Echo.
"That's not something I've been used to at Manchester City. But I don't take that for granted - I really don't.
"If I wasn't playing well and wasn't doing the right things, I wouldn't expect to play."
Both Phil Bardsley and Anton Ferdinand can play at right-back and Onuoha believes Sunderland's strength in depth at the back has played a part in their positive start to the season, which has seen them concede just seven goals in eight games, when the Black Cats have faced the likes of Arsenal, Liverpool, Man City and Man United.
"We've got good competition for places defensively and with the options the manager has, I wouldn't really say I've been surprised, as such, at how well we've done defensively," added the former England Under 21 international.
"When you look around you at the players in the team and in the squad, I think you can see there has always been the potential for us to do well.
"It's just that right now we are finding a blend of players which works well for us."
Bruce made a string of summer signings but an enthusiastic, youthful squad has helped them settle in quickly at the Stadium of Light.
"I'm one of a few fresh faces at the club who have got something to prove and I think we've got a very focused squad as a result," Onuoha added.
"There is a strong team spirit here, and that does make a big difference - especially in a squad that has quite a lot of young players.
"When you've got a young squad - and I mean players in their early 20s and so on - you can develop a sense of togetherness on the field that helps win games."