Of the players listed, I would say Donte Stallworth

Mike McKenzie is just part of a bad defense, but he could improve his games easily.
Carney is good kicker, so his leg is not in question.
Joe Horn, as mouthy as he is, is the only WR on the team that can back his words up with his gameplay. Injuries are never beneficial to a player.
Speaking of which, Deuce McAllister has suffered from injury issue for a while now. He is still a solid RB that can allow for the offense to become more versatile.

Stallworth has yet to develop into the #2 WR as he was projected to become. He has one more season or he hits the road. Donte should already be playing at a point where Joe Horn does not need to be the team's WR workhorse.

None of the players you listed are the Saints' worst player... I would say it is a third string offensive lineman actually.

WOW.... out of the guys you listed it has to be McKenzie.... what has he done... better yet what can he do that about 75 other NFL DB's can't.... he's nothing special.... Stallworth has 4.2 speed, and nobody will admit it... but you know you have to keep an extra eye out for him... and Horn has been a main stay in the league making a name for himself over the years... as far as Carney... he's just another kicker....

John Carney.
You asked.

Deuce McAllister, He is totally overated.

When was the last time he took over a game? Never

Out of the players that you listed i would definetly have to say john carney, because I come from New Orleans and I've seen him mess up too many times, but hopefully hes better next season.

I've never heard of Mike McKenzie or John Carney so they can't be that good.

Mike McKenzie

My vote is for John Carney.

all the above