The Seattle Seahawks host the Philadelphia Eagles on "Sunday Night Football" in Week 13. The Eagles are 3.5-point favorites, down sharply from an open of six.

The Over-Under, or total number of points Vegas thinks will be scored, is 47, down one from an open of 48.

Before you bet on a high-profile game like this with so much Vegas odds movement, you'll want to hear what veteran handicapper Josh Nagel has to say.

When the Seahawks hosted the Falcons in Week 11 as three-point favorites, Nagel told readers to back the underdog Falcons without thinking twice. The result? Falcons 34, Seahawks 31 -- another easy cash.

That continued a trend for Nagel, who is a whopping 8-1 picking Seahawks games since the start of last season -- including 4-0 this year! Anyone who has followed his picks is up big.

Part of his success: a West Coast insider, he's a master at picking Seahawks games, regardless of who Pete Carroll's team is playing. He's won numerous handicapping contests and been in the industry for nearly 20 years. 

Now, Nagel has evaluated every injury, every match-up, and every trend for Eagles-Seahawks and locked in his pick. You can only see it over at SportsLine.

Nagel knows the Eagles boast the league's highest-scoring offense (31.9 ppg), two points more than any other team.

Philly also has the third-ranked scoring defense (17.4 ppg) and the top rushing defense (65.1 ypg) by a healthy 10 yards. They're a league-best 10-1, with their lone blemish coming against the Chiefs way back in Week 2.

Over their last two games, the Eagles have outscored the Cowboys and Bears by a combined 68-12. They've put up over 30 points in five straight and QB Carson Wentz leads the NFL in touchdown passes with 28 against just five picks.

But just because the Eagles have been dominant doesn't mean they cover a 3.5-point spread, especially cross-country in one of the loudest stadiums in the NFL.

The Seahawks have won six of their last eight games, and QB Russell Wilson has been on fire, tossing multiple TDs in six straight. He has 23 passing TDs on the season, good for third in the NFL.

Wilson has also produced with his legs the last two weeks, rushing for a combined 111 yards and two scores. After failing to top 50 yards on the ground the first seven games, Wilson has done so twice in his last four outings.

SportsLine's advanced projection model says Wilson will continue to get it done on Sunday Night Football, throwing for 250 yards and two touchdowns. TE Jimmy Graham has the best chance of finding the end zone.

It's no surprise that Nagel is leaning Over for Sunday night, but what about against the spread, which he's made his name picking?

He knows there's a big x-factor that ultimately determines which side of Seahawks-Eagles you need to back, and data scientist Stephen Oh, who's on a 12-5 NFL run, agrees with him.

So which side should you back in Eagles-Seahawks on Sunday night? Visit SportsLine now to see what big x-factor determines which side you need to be all over, all from the handicapper who's nailed eight of his last nine Seahawks picks, and find out.