It came at a price as William Gallas and Kieran Gibbs both suffered injuries but Wenger was at least happy with his side's response in what is set to be an important week.
"The first half was good, with lots of fluent movement, but after we lacked a bit of urgency in the final third because we eased off," he said.
"If you look in the last eight or nine games, we have had a very good run.
"Saturday at Sunderland was not at the requested level.
"It is not out of the mind of the players because you never forget a disappointment, but it was important to win this game well with the Chelsea game on Sunday in mind."
Arsenal continued their fine record of qualifying for the latter stages of Europe's elite club competition - something Liverpool could not do
"I am pleased, because this competition is not easy," said Wenger, who took his side to the final in 2006 and semi-finals last season.
"We were favourites in this group, which was normal, so we just did the job.
"But if you put the 10 years together, we have been consistent."
Wenger added: "There are two competitions in the Champions League, one is a championship, one is a cup.
"We move into that cup stage now, and that's very different psychologically.
"Every minute now becomes important. We have to adapt to that.
"Let's get all our injured players back, get in a strong position in the Premier League, and that will give us the confidence."
Wenger, meanwhile, confirmed midfielder Alex Song, 22, had agreed a new deal.
"We extended his contract yesterday (on Monday)," added the Frenchman. "That will be confirmed very shortly.
"He is an important player.
"Alex has three years to go, now he has four years to go at the end of the season - to 2014."
Standard, meanwhile, must now hope the Gunners beat Olympiacos, with what is set to be a much-changed young side, to stand any chance of claiming runners-up spot.
The Belgians were missing main striker Milan Jovanovic through injury, but could have taken the lead when Dieudonne Mbokani smashed his drive against the angle.
However, Standard finished with 10 men when Mehdi Carcela-Gonzalez was sent off for pushing his forehead into the face of Arsenal captain Cesc Fabregas.
Standard coach Laszlo Boloni was less than impressed by the 20-year-old.
"That has serious consequences for us," he said.
"I am gutted about his behaviour and angry against the lack of respect towards his team.
"The club have put a lot of effort to push him where he is now, in the Belgian national team.
"I will not give him an easy time.
"He has to understand the responsibility of the club is more important than his own stardom."
Boloni added: "We were prepared for the pressure Arsenal would put on us, and we tried to have more density in midfield, which is not easy with the one-touch football they play.
"However, they could not score from the chances they had in front of goal.
"We also missed some chances, especially in the first half.
"But with all the injuries we had, and the quality of the opponent we cannot allow to give the ball away. If you do that, it is very frustrating.
"We needed to be more focused."