Week 15 of the NFL schedule begins when the San Francisco 49ers visit the Seattle Seahawks on Thursday Night Football at Lumen Field. The 49ers (9-4) lead the NFC West, but are trailing the Eagles (12-1), Cowboys and Vikings (both 10-3) for the best record in the NFC. The Seahawks (7-6) trail the 49ers by two games in the division. 

Kickoff is set for 8:15 p.m. ET. San Francisco is a three-point favorite in the latest 49ers vs. Seahawks odds from Caesars Sportsbook, while the over/under for total points scored is 43.5. Before you lock in your Seahawks vs. 49ers picks or NFL predictions, you'll want to see what SportsLine senior analyst Josh Nagel has to say.

Nagel is a Nevada-based handicapper with more than 20 years of experience in the sports wagering industry. SportsLine's assistant managing editor has covered the wagering industry on a variety of platforms and has won numerous sports handicapping contests. He has hit 54% of his NFL spread picks (749-636-22) since the start of the 2016 season. 

In addition, Nagel has gone an OUTSTANDING 19-6 in his last 25 spread picks involving the Seahawks! Anyone who has followed him is way up.

Nagel knows that San Francisco arguably has the best defense in the NFL. The 49ers lead the league in scoring defense (15.2 points per game) and total defense (286.8 yards per game). The 15.2 points per game average is the second best of any team since the start of the 2014 season, behind only the 2019 Patriots (14.1).

Nagel also knows that quarterback Geno Smith is having a career year. The 32-year-old signal-caller already has set career-highs in passing yards (3,433) and passing touchdowns (25). His passer rating (106.8) also would set a career-high. Led by Smith, Seattle ranks sixth in scoring offense (26.3 points per game).

Now, Nagel has locked in another confident against-the-spread pick for 49ers vs. Seahawks. We can tell you he's leaning Under the total, but he knows a crucial X-factor makes one side of the spread a MUST-BACK! You ABSOLUTELY need to see what it is before locking in any picks of your own.

Who wins 49ers vs. Seahawks on Thursday Night Football? And what critical X-factor makes one side of the spread a must-back? ... Join SportsLine right now to see which side of the Seahawks vs. 49ers spread to jump on, all from the expert who is 19-6 on picks involving the Seahawks!