Backdoor covers happen all the time in football wagering, but Sunday they were particularly impactful regarding two games.

For the record, a backdoor cover is when an underdog scores what are essentially meaningless points at the end of the game — meaningless in the sense that the scoring doesn’t change the game's result — but do influence the point-spread betting outcome.

In two heavily bet NFL games, Kansas City at Miami and Green Bay at Detroit, late field goals allowed underdogs to close the point-spread gap and cover. In both cases, the decisions helped the books and worked against the public.

The Dolphins kicked a field goal with 16 seconds left in their 33-27 loss to Kansas City as a 7-point underdog, thus covering by a point. Miami trailed by nine points as they started their last offensive possession. The drive stalled at the Chiefs’ 26-yard line and, playing the chess match by the book, Miami sent in kicker Jason Sanders to boot a 44-yard field goal. Subsequently, Miami failed on its longshot onside kick.

The Chefs were carrying 91% of the point-spread handle at PointsBet; 76% of the points-spread money on FanDuel, and 78% of the point-spread handle at William Hill (K.C. also had the largest percentage of tickets, 12%, of any team at William Hill on Sunday).

Similarly, Detroit was a 7.5- to 9-point ’dog against Green Bay. The Lions trailed by 10 points, 31-21, when they marched to the Packers’ 14-yard line late in the fourth quarter. Following the same script as Miami, the Lions sent in Matt Prater to kick a 32-yard field goal with 1:49 left to narrow the score to 31-24, and also attempted what turned out to be a futile onside kick. Green Bay had 79% of the point spread handle at PointsBet; 83% of the points spread handle at William Hill and 89% of the spread handle at BetRivers.

Parlay Bets Take a Hit

Those two backdoor covers against popular favorites, along with Philadelphia’s 24-21 upset of New Orleans (-7.5), crushed many a parlay betting ticket and allowed the books to salvage what amounted to a choppy break-even day after stomping the betting public for the previous five or six weeks.

“That’s the problem with laying points, you can get burned at the end like that,” said Johnny Avello, DraftKings’ head of sportsbook operations, of the backdoor covers.

“But the luxury of betting the underdog,” Avello added, “is that they can win the game two ways — they can win it straight-up or they can cover the spread. So, with the underdog, you have two ways to win. With the favorite, you just have just the one way to win.”

As both the defending Super Bowl champ that’s been scoring tons of points (31 a game) and running up a 12-1 record so far this season, the glamorous Chiefs have become the betting public’s darling.

“So, it knocks off a lot of parlays whenever the Chiefs don’t cover,” said Jeff Stoneback, director of trading for MGM Resorts. “We certainly would have had some parlays tied up with Seattle (a 40-3 victor over the winless Jets) so that (backdoor cover) saved us.”

The mega-betting had been quiet in recent weeks but retuned Sunday, at least at BetMGM.

“We had one player that hit a $120,000 parlay that won him $247,000 (L.A. Rams over New England from Thursday, plus Tennessee over Jacksonville Sunday) and then he had a $160,000 parlay which won him $329,000 (Titans plus Tampa Bay over Minnesota),” Stoneback said. “He hit us for half-a-million so we were a loser in the (early window games) but we wound up getting most of the money back later.

”The Eagles game was huge for us with them beating the Saints and then the Lions covering against the Packers. Those two almost got us even.“

Winning Games for Bettors

It wasn’t all gloom-and-doom for the bettors, though. Public-backed winners included Tennessee, Dallas, Seattle, Indianapolis, Tampa Bay and Arizona. For the Cowboys (-3), their 30-7 triumph over Cincinnati was only their third win against the spread this season and the first as a favorite.

The public got in some last licks in the Sunday Night Game favoring Buffalo (moderately) over Pittsburgh; the Bills (-2) won, 26-15. Earlier in the week, MGM took a $220,000 wager on Buffalo at -1.5. Also, as the Bills were in the process of handling the Steelers, a William Hill New Jersey bettor placed a $50,000 LIVE InPlay wager on Buffalo (-145) to win a payout of more than $84,000.

NFL Betting Odds & Ends

William Hill reported a couple of bettors cashed in on the rare Eagles’ victory: one bettor took Philadelphia on the money line at +280 and turned $500 into $1,900, and another took the Birds at +250 on LIVE InPlay to turn $4,000 into $14,000.

In prop betting, DraftKings reported that Denver’s Dionta Spencer returning a punt 83 yards for a touchdown against Carolina earned at least one bettor $505 on a modest $5 first-touchdown wager.

Similiarly, BetRivers.com reported that several Colorado BetRivers.com customers also hit on Spencer’s punt return winning $1,010 on $10 wagers.