The Gunners take on the current holders at Wembley Stadium on Saturday with a place in next month's final at stake.
Despite admitting that Wigan are capable causing an upset on the day, Gnabry believes that Arsenal have every chance of progressing.
"It is going to be difficult. Wigan will do their best to win the game as well to get another shock in against a Premier League team," he told the club's official website.
"It is going to be a fight but we should face it as any other normal match: don't be scared because they are in the [Championship].
"We should be favourites and if we play our normal game, there should be no doubt that we can win it."
Arsenal reached the semi-finals by beating Everton 4-1 in the last round.