The Arizona Cardinals host the Dallas Cowboys on "Monday Night Football" in the final game of Week 3.

There has already been plenty of line movement in this prime-time showdown. The Cowboys are three-point road favorites, meaning Vegas thinks they'll win by three. That's down a half-point from where it opened.

The over-under is 47, meaning Vegas thinks 47 total points will be scored. That's down a half-point from its open of 47.5.

Both teams have major question marks. Cowboys running back Ezekiel Elliott is coming off a career-low 8 yards rushing against the Broncos, while the Cardinals lost do-it-all runner David Johnson in Week 1.

In a game like this featuring so much uncertainty, you'll want to hear what Mike Tierney has to say.

Tierney went a sizzling 22-9 on NFL over-unders last season. And he has gone an impressive 5-2 this season, including nailing the under on the Cowboys' Week 1 prime time game against the Giants.

Part of his success: He's full of inside information. He has reported from seven Super Bowls and is a well-known national sportswriter. Anyone who follows his picks has been well-rewarded.

Tierney knows Dak Prescott is suffering from an ankle injury, but is expected to play. And he knows Elliott had never had fewer than 50 yards rushing until last Sunday; that came against the same Broncos who held Melvin Gordon to 54 yards in Week 1 and LeSean McCoy to 21 yards on Sunday.

He also knows the Cardinals have struggled offensively without Johnson. They mustered 16 points against the Colts a week ago, and that took overtime. But just because both teams are facing uncertainty on offense doesn't mean "Monday Night Football" goes under.

Cardinals receiver J.J. Nelson broke out last week with a 5-120-1 stat line, and he's questionable for Monday Night Football. Carson Palmer threw for over 300 yards. Arizona still has Larry Fitzgerald, who has nine catches this season, and may get TE Jermaine Greshman back after he sat out last week's game with an injury to his ribs.

Elliott, meanwhile, shined as a receiver against the Broncos with four catches and Jason Witten led the NFL with 17 receptions entering Week 3. This game will be played in perfect conditions in front of a national audience, giving both offenses an opportunity to get back on track. And any defensive and special teams scores also count for the Over-Under.

Tierney is leaning on the Cardinals to cover the spread, but what about the over-under, which he has made his name picking?

He knows there's a huge x-factor that ultimately determines whether Cardinals vs. Cowboys on "Monday Night Football" goes over or under. And SportsLine Data Scientist Stephen Oh, who has won his three of his last four total plays, agrees with him.

So which side should you back in Cardinals-Cowboys on "Monday Night Football?" And does this game go Over or Under? Visit SportsLine now to see what big x-factor sends Cardinals-Cowboys over or under, all from the expert who is blistering hot in total plays, and find out.