Arsene Wenger said that Arsenal have to win their Champions League match at home to Olympiacos Piraeus on 29 September. The Gunners lost their opening Group F encounter at Dinamo Zagreb 2-1 and while it is only the second round of matches, Wenger knows that his side cannot afford to drop points at the Emirates.

"You have to win your home games if you want to qualify in the group stage, it's as simple as that," the Frenchman told a news conference at Arsenal's London colney training ground northwest of the capital.

"We have an opponent, we cannot afford to drop points against anybody at home."

The opening round of Champions League matches saw three of the four English clubs in the competition losing, with only Chelsea managing a victory. Wenger thinks the intensity of the Premier League is the main reason.

"You cannot say we are at that level now because in the last two years Barcelona won the Champions League and the year before it was Real Madrid who won the Champions League, so you have to say they were the better teams. But are we far, I don't think so but we have to show that with our results," he said.

Olympiacos top the Greek Super League with a 100 percent record after five games, their domestic superiority enabling them to spend more time on preparing their side for the Champions League.

"Olympiacos dominates their league, it's a team with a big advantage, they dominate easily their league at the moment so they can prepare for these kind of games," Wenger said.

"They know how to compete in the Champions League, they are well organised, some players who know the Premier League."

With Olivier Giroud suspended, Arsenal will be boosted by Alexis Sanchez's timely return to goal-scoring form. The Chilean rediscovered his spark with a hat-trick as Arsenal moved into the Premier League's top four with a 5-2 victory in an action-packed game at Leicester City on Saturday.