A little late but my thoughts on Sproles are that he was the safe veteran. There was no chance he was going to fumble and no chance he'd decide to try and bounce something outside for an extra 1/2 yard and end up out of bounds. There was also a good chance his presence would 'fool' the Bears. I know in his last couple of years with the Saints teams used his presence on the field as a signal the Saints were passing and they'd disregard the run. Maybe the Eagles were hoping to get the Bears with 6 DBs in?
We had a good party here Sunday for what turned out to be the only half way exciting game. I was surprised the Eagles threw at Lattimore. My opinion is he's the best CB in football and most teams just don't throw at him, especially if the can get a slot WR or TE on Williams. I don't know if Foles didn't see the switch, or just ignored it but to me the game flipped when he threw the first interception to Lattimore who was 1 x 1 with Ertz. Maybe he thought it was WIlliams in coverage I don't know. After that point the Eagles had 92 yards in offense and the Saints had 397.
One thing I've learned about Dennis Allen is his defense seems to always come in and have a rough start. Doesn't seem to matter who they play, teams have success to start the game. He makes adjustments though, just not sure why he can't seem to start a game off well.