Redknapp told The Sun: "The most obvious thing was that United are streets ahead of Arsenal - they have now beaten them six times out of the last seven.
"United are going to be right there again, but you fear for poor old Arsene Wenger because he has lost so many top players.
"You lose the likes of Cesc Fabregas, Robin van Persie and Samir Nasri and it's going to hurt like hell, and Arsene must have feared Van Persie would cause him pain.
"That's exactly how it worked out, and you just knew from the moment he scored the opener that Arsenal weren't going to get anything out of the game.
"Arsene has tried hard to paper over the cracks, but the only player he has brought in that you could mention in the same breath as the ones he has lost is Santi Cazorla.
"They're nine points behind United already, and the gap is going to get a lot bigger before the season is over."