Arsene Wenger's men followed up their 6-0 drubbing at the hands of Chelsea with a 2-2 draw at home to Swansea City on Tuesday, a result that leaves them six points adrift of the leaders.
A return of just eight points from seven matches has seen Arsenal slip to the periphery of the title race, while even a top-four finish is now under threat as a result of Everton's four-match winning streak, and Campbell feels that the defeat to the Blues was the hammer blow to their hopes.
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"A miracle has to happen [for Arsenal to win the league], for the other teams to lose games, for them to win games, for it to all change around.
"Mathematically it's still there [but] the whole momentum of them trying to get back into winning the Premier League has definitely been dented and I think it could be gone now."
Campbell, who lifted two Premier League titles and three FA Cups during his time with Arsenal, believes that Wenger will have been badly affected by the recent dip in form and says that the cup must now be a priority for his former club.
"I think he will be definitely hurt," he remarked of the long-serving manager. "It's a special time when you get 1,000 games [at the same club] and you always want to end in a happy way or have a good result. Obviously that didn't happen so I'm very, very disappointed and he'll be deeply hurt.
"I think he'd like to end with a win under his belt this season.
"Definitely the FA Cup is the only thing to really, really go for and they can't miss that chance because it's a special cup and I hope the players treat it as a special cup and respect the team they're playing against [Wigan] because that's the beauty of the cup; if you disrespect it, it can really turn around."