what defense should i start?

I'd start the 49ers D/ST. The lions special teams is awful (they give up almost 100 kr yrds/game) and Ted Ginn, Jr. is having a great season so far.

First of all, are you carrying 2 defenses? If so, do you have to? If you don't it's a waste of a roster spot.

I would pick the Saints this week as they face a struggling Bucs offense, one that will likely be without their biggest weapon in Blount.

The 49ers face a potent offensive attack with the Lions...they will smother the Lions' running game but the Lions have other weapons to score at will...you could put 3 guys on Calvin Johnson and he still has a (very good) chance at coming up with the football.

I would play the Bengals (vs. the Colts) over both of these defenses this week...and I might play the Bills over the Saints this week too.

The 49ers have a bye next week...and the Saints have some favourable matchups in the coming weeks...so I would drop the 49ers and keep the Saints...use that roster spot to take a chance on someone...pick up Greg Little, Jackie Battle, Tim Tebow, Heyward-Bey...Defense/Special Teams might win you the odd week but they don't figure into the entire scheme...there will always be a good matchup to exploit week-to-week... there are few defenses that I would hold onto in fantasy land and the Saints and 49ers are not among them...I would only hold the Saints because of upcoming matchup potential.

I'd play the Saints D just because I don't feel comfortable playing any D against Detroit right now. San Fran might be good against the run but they're not so good against the pass.

New Orleans, I have a feeling that Stafford to Johnson will make that game into a field day.. The niners never really addressed the cb position in the off season and Lions line is better than those that SF has played..

Go with the Saints.

The Tampa offense is a mess and Blount thier starting RB is out this week.

Detroit's offense is too explosive.

Saints. Lions offense is too explosive while stafford is healthy