Arsenal travel next week to Barcelona in the Champions League and United in the FA Cup quarter-finals but with the league title now back in their hands they must not slip up on Saturday against a team who held them to a 1-1 draw earlier this season.
"It is, until now, the biggest week in the season but if you want a big week in your life you must start well and we start with Sunderland," Wenger told a news conference on Friday.
"We will go for that game without thinking about anything else. Our focus is on Sunderland and the championship is our massive target."
United's defeat at Chelsea means Arsenal are four points behind with a game in hand, and still have to host Alex Ferguson's team who face Liverpool at Anfield on Sunday.
"The league is a vital race - for us, the most important," he said. "It will be interesting until the end of the season.
"It depends on us and how consistent we are. That will decide the championship. We have been on a very good run if you look at our last 10 games and if we maintain our consistency we have a chance."
It is the opposite for Sunderland who, after some impressive results earlier in the season, have lost their last four league games.
"Their confidence has dropped so let's take advantage of that," said Wenger. "We will try to test them, put them under pressure and score goals. I am confident we can always score."
Arsenal bounced back from Sunday's League Cup defeat by Birmingham City to thrash Leyton Orient 5-0 in the FA Cup and Wenger said he was delighted with the attitude of his players.
"You could see on Wednesday that this team is mentally very strong and hungry for success," he said.
"How they responded from the disappointment of Sunday is remarkable."
