The situation in Chicago is dire - the o-line is godawful and Forte regressed last year. Cutler is still going to throw a zillion picks (but he'll probably get a lot of yards, since they'll be playing from behind frequently). Don't put too much stock into the numbers from last week, the Lions secondary is still one of the worst in the league.
Drew Brees is one of the top 2-3 fantasy QBs in the league and I wouldn't trade him for anything less than another superstar
edit: Cutler also basically has no receivers.