ORCHARD PARK, N.Y. — In many ways, the running game is the key to the Patriots’ offense. It sets the passing game in motion. It sets up play-action. It’s like the secret sauce for Tom Brady because it makes the high-powered attack so much harder to defend.

In the four-game stretch leading up to Monday night’s 25-6 win against the Buffalo Bills, the run-pass blend was perfect. It couldn’t get much better, as the Patriots ran effectively with Sony Michel and James White, while Brady and his receivers were sharp in dialing up 30 or more points each week.

Monday night, the mix was off. There was no Michel against the Bills. He was out nursing a left knee injury after a scary episode in Chicago, where he twisted it awkwardly on the first play of the second quarter. The good news for the Patriots is the rookie running back, who was coming off back-to-back 100-yard-games, is expected to return, perhaps as early as Sunday against the Packers.

Without him Monday night, however, there was little semblance of a running game. There was also little semblance of scoring from the offense. The game was in doubt until Devin McCourty’s late pick six. Coincidence?

In place of Michel, the Pats used Cordarrelle Patterson in the backfield. In the first half, he was their leading rusher with 9 yards on four carries. Next on the list? That would be Brady with 8 yards on one carry.

It wasn’t pretty. A lot of that had to do with the Bills, of course. They came in with the 13th best rushing defense in the NFL, and they were tough up front.

“They’re a good defense. They made it tough on us,” White said. “We just have to do a better job as runners, finding those lanes, taking those 4-yard gains, and not being one dimensional as an offense.”

Their 76 yards on 25 carries basically made them one-dimensional.

The Patriots still managed 108 yards on the Bears last week with White and Kenjon Barner doing most of the damage with career highs in carries. It didn’t seem outlandish to assume they might do the same against the Bills. Given how well their offensive line has been playing lately, the Pats have been able to gain yards on just about anyone.

Were they saving White and Barner in this game? Barner only had two carries for 4 yards.

They probably figured they could get by the Bills and produce yards on the ground in other ways.

Julian Edelman took a pair of jet sweeps for 13 yards. Brady was his lead blocker on one and got wiped out by Lorenzo Alexander.

“I was like a speed bump,” Brady cracked. “I wouldn’t say that was necessarily a block.”

White’s carry total eventually rose, and so did Patterson’s. He finished with 38 yards on 10 attempts. He broke one in the fourth quarter for 22 yards. It set up the Patriots’ lone offensive touchdown, with White going in from the 1.

But ultimately, it was obvious they missed Michel. There was no mystery. The Bills’ defense knew Brady was going to throw the ball with no lead back to do the dirty work.

The Patriots relied on other devices, namely the no-huddle and Brady hitting his go-to-guys – Edelman, White – in the clutch, to put themselves in position to pull this game out.

That was made tougher by swirling wind conditions.

“It was pretty windy,” Brady said. “It was weird … the ball was moving weird, almost like a knuckleball to receivers. But it wasn’t terrible. I’ve played in worse.”

Brady finished 29 of 45 for 324 yards. He had no touchdowns. This was a far cry from the high-flying, high-scoring offense of the previous four weeks.

Without Michel, without a legitimate running game, the offense just doesn’t operate the same. They struggled mightily Monday night.

“You can’t be one-dimensional in this league. You have to be able to run the football,” White said. “There’s good defenses in this league. You still have to have balance.”