Why are the Chargers not underachieving? Philip Rivers’ hot start is the primary reason. Rivers has completed 69 percent of his passes with 17 touchdowns and three interceptions. Rivers’ turnovers and special-teams blunders were big problems for the Chargers in recent seasons.

The Los Angeles defense has been solid despite the absence of Joey Bosa. The injury excuses were available, but the Chargers have not needed them. Outstanding quarterback play can carry a team a long way, and Rivers is overcoming coach Anthony Lynn’s weaknesses.

Pete Carroll is doing an impressive coaching job in Seattle. Despite losing several big names, the Seahawks rank No. 5 in total defense (327.3 yards per game) and No. 4 in scoring (18.7 ppg). Chris Carson is powering Seattle’s fifth-ranked rushing offense (134.7 yards per game), and the transition to a run-based attack has helped the line better protect Russell Wilson, who has 16 touchdown passes and is taking fewer sacks.

Oddsmakers and some handicappers have been slow to catch up to Seattle’s improvement. The Seahawks were a steal as three-point underdogs at Detroit last week.

The play: It’s tough to go against Rivers’ hot hand, but lay 1¹/₂ points with Seattle, which nearly upset the Rams on this field a month ago.

Matt Youmans is co­-host of “The Edge,” weekdays 3-­5 p.m. Tune in at VSiN.com, fuboTV and SiriusXM 204.