The Hammers were thrashed 5-1 at home by Chelsea last night after being thumped 3-0 at Sunderland last week in their Premier League opener.
Calling Friday's game for BBC Sport, Redknapp said: " If I'm Sunderland, Burnley, Leeds, I'm looking at West Ham and thinking 'they're the ones, they're the weakest team in the Premier League we're going to catch'."
On manager Graham Potter, Redknapp said: "I think he's playing with a three because he doesn't trust any of them in a back four. Everyone defensively, nobody really looks like a leader or taking any kind of responsibility. It was a really bad unit, all of them just didn't play to the level they should be.
"That squad isn't good enough. They haven't got enough good players. That midfield just couldn't get near, they didn't have the legs to get around.
"They need to get someone with real legs. It's no disrespect to them, it would have been hard for any team to play against Chelsea, but they need to get numbers otherwise this will be an incredibly long season."