Alexis Sanchez scored both goals at the Emirates as the Gunners moved to a point behind fourth-placed Liverpool and three behind third-placed Manchester City.
Liverpool hosts already-relegated Middlesbrough on the final day of Premier League while City goes to Watford and Arsenal is at home against Everton.
And Wenger told Sky Sports: "I still think City are in it, they go to Watford, which is a difficult place to go."
"What you want is for everybody to fight like Sunderland did tonight. Then you accept your result, that's it. You have to give Sunderland credit, they tackled for every ball, didn't try to waste time at 0-0, and they had fight."
With empty seats around the Emirates, It looked like being a frustrating evening for Arsenal as Sunderland goalkeeper Jordan Pickford kept them at bay.
"It was important to keep our nerve and keep our composure," said Wenger. "And we became stronger in the last 20 minutes and managed to win the game and that's what you want, so I must say well done.
"Sanchez was maybe not completely 100 per cent tonight but he dug deep. I want to give credit also to the players who gave him the ball, Mesut [Ozil] and [Olivier] Giroud, and a good ball from [Granit] Xhaka to Ozil."
"He just had to tap it in but he knows where to be and that's not easy."
Asked about the number of fans who stayed away from the game, Wenger said: "We have to focus on our job, not looking at how many people are in the stands. When you play football you want to play ideally with a packed stadium, but we are quite spoilt with that overall. It's a Tuesday night maybe, people think Sunderland is an easy game, so there were less people."