Arsene Wenger's charges are set to go up against Hull City at Wembley, bidding to win their first piece of silverware for nine years.
However, Mertesacker believes brandishing Arsenal as failures should they lose the showpiece would be an overreaction.
"That would be a bit harsh," Mertesacker told The Sun. "It wouldn't be a disaster, but our expectations are now absolutely to win the cup.
"I am not here to say that I believe we are going to fail."
Arsenal had to rely on penalties to come through their semi-final clash with Wigan Athletic last month, and Mertesacker believes that experience could have an impact on next weekend's clash.
"You also have the pressure that came in the semi-final, and it will come back in the final," he added. "But I think we have raised our confidence that much in recent weeks that I think we want to make it.
"Now we want to finish the season properly."
