Quarterbacks usually are the focal point. But give a close look to the trenches and that each team will be missing a key skill position player. When doing that this matchup spells Under to me. 
The Chargers rank 13th in scoring defense. They have a premier pass rusher in Joey Bosa, good run-stuffing linebackers and a solid secondary. Michael Thomas will be missing his fourth straight game. There's a big drop from Thomas to the Saints' other wide receivers. Offensive tackle Ryan Ramczyk is questionable after suffering a concussion last week. 
New Orleans ranks sixth in run defense and 14th in pass defense. This is rookie Justin Herbert's first NFL dome game and just his second road start. He won't have Austin Ekeler, the Chargers' best running back, nor will he have his three best offensive linemen. Center Mike Pouncey is done for the season. Right tackle Bryan Bulaga and right guard Trai Turner have been ruled out for this week. 
This means the Chargers have backups at three spots and their two left side offensive line starters, Sam Tevi and Forrest Lamp, are below average. Tevi ranks among the league's worst in missing pass blocks. Saints star pass rusher Cameron Jordan has the second-highest pressure rate in the league among defensive linemen. 
Despite being in different conferences, the teams have a familiarity. They have faced each other in joint practices the past couple of years. This should be a plus for the Under as neither team figures to get caught off-guard.