Seattle at San Francisco Sunday, 4:05 p.m. EST, Fox BetMGM NFL odds: 49ers by 6 1/2. 49ers player to watch QB Brock Purdy threw for 353 yards and two TDs last week against Tampa Bay and had his 13th career game with a rating of at least 115. Key injuries The Seahawks activated RT Abe Lucas off the PUP list …