The bookies say it was the biggest upset in the legalized sports-betting era.

The Detroit Tigers on Wednesday went into Houston, used four pitchers, managed just two measly hits, and still beat Justin Verlander and the Astros, 2-1.

Even the Tigers’ Twitter account acknowledged the remarkable feat.

Detroit opened as about 4-1 underdogs, which is quite high for baseball. That number would only grow. The Tigers were sending out Daniel Norris (3-10, 4.82) against Verlander (15-4, 2.86). Detroit entered the night 37-86. Houston was 81-46, 45-15 at home. The outcome seemed inevitable.

Seemed.

When two bettors placed nearly $120,000 on Houston at MGM properties, the Astros’ odds kept rising. There was one bet of $55,000 to win $10,000 on the Astros, another of $63k to win $11k.

“Now we are at unprecedented -600,” MGM’s Scott Shelton told Patrick Everson of the sports gaming website Covers.com. Minus 600 is equivalent to 6-1.

MGM’s number grew to -770 by first pitch, according to a screengrab tweeted by gambling reporter Marc Meltzer. A baseball line of -770 is like an NFL team laying 25 points. Maybe 30.

For comparison, the Red Sox were around -160 last night. The Phillies were +150.

“I’ve seen some lines approaching -500,” Inquirer handicapper Vegas Vic said Wednesday night. “But never anything like this.”

FanDuel said it got hurt by Detroit’s win.

“We had more wagers of $1,000+ on the Tigers moneyline than we did on the Astros during the entire game,” spokesman Kevin Hennessey said. Eighty percent of their bets were on the Tigers at either at +470 pregame or +500 during the game.

The Tigers scored on solo home runs by Ronny Rodriguez and John Hicks (ninth inning). With one out in the bottom of the ninth, MGM’s app had Detroit as -770 favorites. The game’s ending just added to the night’s insanity.

It’s not easy for a hitter to go 4-for-4 and make the final out of the game, but that’s what Houston’s Robinson Chirinos did. He drilled a double into the gap and was thrown out at third going for the cycle.

Dave Tuley, senior reporter for the Vegas Stats & Information Network, said the average closing price in Sin City was Tigers +430, Astros -550.

Tracked by the Inquirer, the Astros were -556 on MGM’s New Jersey app entering the bottom of the eighth when the game was tied. Going into the bottom of the ninth, after Hicks’ homer gave Detroit a 2-1 lead, Houston was +160. That’s quite a swing.

On Aug. 11, the Astros closed at -460 with Verlander against the Orioles +370. Baltimore hit a two-run homer to win that game in the bottom of the ninth.

Professional gambler Jack Andrews said it best when he tweeted Wednesday, “Someday, I’ll tell my grandkids about MLB 2019. It’ll be the answer to the question of ‘Grandpa, why do you have gray hair?’ "