I think it's good to look back on previous week to see if there were glaring mistakes in capping, but I'm more one for the actual games, injury reports, home field, defensive schemes, etc. over how a team has been doing ATS. Week 6 was crazy weird/bad though for me (and it seems for others as well).
One of the problems with betting on the NFL besides the variables of turnovers, officiating and injuries is that it seems to be trendless but you can make an argument that there is something close to parity right now so that favors dogs. After last weekend, I 'trust' no NFL team, after S.F. and Houston both got blown out at home.
In the long run, most people trying to actually make money betting on sports would be much better off taking those gambling funds and opening up a small brokerage account somewhere with a good commission rate on a small number of shares -- say, Interactive Brokers with $1 commission on up to 200 shares -- and VERY slowly buying an index like the SPY ETF after weakness in the market and then slowly selling after the inevitable strength in the market. Repeat often and never let your 'inventory' of owned stock get too large. I digress .....
Even with teaser points, I see little to like this weekend but am focusing on point totals. You'd think I wouldn't do that after an unbelievable number of points were scored off of turnovers in the Denver/S.D. game, ruining my U54 teaser on that, which was amazingly a winner until Rivers threw that last TD interception with 2 minutes left. The early fumbles by Denver special teams totally changed the tone of the game.
Just for grins this week I have a teaser - $2 on Seattle +15 and the O30 Vs. the Niners, which should be a fun game to watch.