The Giants and Jets meet Friday night at 7:30 p.m. ET in the battle for New York at MetLife Stadium. The Giants won by one in a 32-31 thriller last year on the strength of two interception returns for touchdowns. It's technically a Jets home game, and Gang Green is favored by 2.5. The Over-Under, or total number of points Vegas thinks will be scored, is 41.5. Bettors from around the world will be locking in wagers on this high-profile game, so before you make any Giants vs. Jets picks, you need to see what SportsLine's Mike Tierney has to say.

Tierney knows the NFL. A national sportswriter whose work appears in the New York Times and Los Angeles Times, he has reported from seven Super Bowls. Tierney excels both against the spread and straight up, gaining valuable insight covering the NFL and other major sports up close that you can't find anywhere else.

Tierney has been a winner for SportsLine members in every sport, but the NFL has proven to be his specialty. Last year, his expertise led to an astounding profit of more than $16,000 for $100 bettors who followed his plays. That record includes a perfect 4-0 mark in ATS picks involving the Giants.

We can tell you Tierney likes the under for Friday's Giants-Jets showdown, but he has unearthed the critical x-factor that will determine which side of the spread hits hard. He's sharing his pick, and the key reason for it, only over at SportsLine.

Tierney knows the Jets' defense has allowed just 15 points in two preseason games, lowest in the NFL. Such defensive success would be a welcome change from last season, when the team finished 24th in overall defense and 22nd in points allowed.

But the team's big story in preseason has been at quarterback. Rookie Sam Darnold has vaulted up the depth chart and is expected to get big minutes Friday in a regular-season tryout. He's 21 of 29 for 158 yards, one touchdown and one interception in two games.

Teddy Bridgewater, who has been the center of trade rumors the past week, has shown his mettle in preseason as well. He has gone 17 of 23 for 212 yards and two touchdowns.

The Giants have gone 1-1 in the preseason led by reserve QB Davis Webb, who is 23-for-42 passing for 210 yards. Eli Manning is just 4-for-7 for 24 yards, but is expected to see significant action Friday. Manning had 121 yards and a pick last year in this game.

He may be without RB Saquon Barkley and WR Odell Beckham Jr. Barkley, the heralded first-round pick, was back at practice Thursday after battling a minor hamstring injury, but is unlikely to play Friday. Barkley has managed just four rushes so far, but Robert Martin has been a capable option, with 12 carries for 86 yards.

Beckham is also questionable to suit up for the first time since breaking his left ankle on Oct. 8, but the Giants should get solid defensive play, as linebacker Landon Collins said many of the regulars will play three quarters.

So what is Mike Tierney's strong against-the-spread pick on the Giants-Jets? And what major x-factor determines the outcome? Visit SportsLine now to see which New York team is a must-back, all from the man who brought in more than $16,000 for $100 bettors last season, and find out.