Defender Laurent Koscielny returns from injury as Arsenal attempt to overturn a two-goal deficit against Barcelona in the second leg of their Champions League last-16 tie.
The Gunners trail 2-0 from the first leg and must score twice at the Nou Camp to have any chance of progressing.
"We don't have to calculate too much, we know we have to attack and score," said Arsenal boss Arsene Wenger.
"The players are united to give a strong performance."
The tie was finely balanced for most of the first leg at Emirates Stadium, but two Lionel Messi goals in the final 20 minutes put the Spanish champions firmly in control.
"Our approach was not bad in the first leg but we lost our balance and got caught," said Wenger.
The Gunners boss has come in for renewed criticism as Arsenal's pursuit of trophies domestically and in Europe has suffered a series of setbacks.
But the Frenchman, 66, remains as dedicated as ever to bringing success to the club.
"I am even more motivated than the day I arrived," he said. "When you are a long time somewhere, people always question you. I don't question my dedication, it is 100%."
He added: "We have gone through a disappointing spell and it is important to remain calm and strong."
Barcelona boss Luis Enrique, whose side are aiming to become the first team to retain the Champions League trophy since the old European Cup was rebranded in 1992, had supportive words for his Arsenal counterpart.
Asked if he could imagine replicating Wenger's 20-year stay at one club, he said: "In the modern era, it is impossible.
"It means Wenger is a very good coach. No one doubts that and only the chosen ones can be such a long time in one club."
Barcelona, on a 37-game unbeaten run, are strong favourites to reach the last eight, but Enrique says his team will not take anything for granted.
"We want to be better than Arsenal on Wednesday," he said.
Messi, Luis Suarez and Neymar are all expected to start for Barcelona.