Pat Surtain II suiting up on game day has felt like a guarantee for the Broncos since his rookie season in 2021. The team is expected to enter a new reality on Thursday night.

Denver’s All-Pro cornerback hasn’t missed a game since Jan. 8, 2022, when the Broncos faced Kansas City in the final week of the regular season. Since then, he’s played in 40 straight games, but that streak could end against the Saints due to a concussion that kept him out of Tuesday’s walkthrough practice.

Unlike Sunday’s loss to the Chargers when defensive coordinator Vance Joseph had to make adjustments on the fly, he has time to prepare for life without Surtain on prime time at the Superdome.

“Pat allows us to do things in coverage that most players can’t,” Joseph said. “Having a couple of days to adjust your plan (for) players, it’s always an advantage.”

It didn’t take long for Joseph’s game plan to get altered against Los Angeles.

On the team’s very first defensive snap of the day, Surtain was covering Ladd McConkey when he hit his head on the turf. The Alabama product was immediately taken out of the game and later ruled out with a concussion.

Joseph said losing a cornerback like Surtain is harder to overcome than losing a defensive lineman. He often lines him up against the opponent’s best receiver and uses Surtain’s presence to push the ball in the direction Joseph wants it to go.

Herbert, who finished with 237 yards passing and a touchdown, found holes in the middle of the field to exploit once Surtain went down on Sunday. As a result, Denver struggled to get off the field on third down.

“We had a game plan with (Surtain) being out there for us, so adjusting that part was the biggest deal,” Joseph said. “Losing Pat and not winning on third down set us on a tailspin.”

Denver made the right adjustments, allowing just three points in the second half. But too much damage was done in the first two quarters.

Surtain’s absence also meant players had to step into new roles. Ja’Quan McMillian had to split time at nickel — his primary position — and outside cornerback. McMillian usually only gets a couple of practice reps at outside cornerback over the course of a week, so it took him some time to get comfortable.

“The biggest thing was space-wise. You got a lot more bodies (around you ) in the slot, but on the outside, you are on an island,” McMillian told The Post. “If it comes around again, I’ll be more prepared.”

Joseph said it’s beneficial to have a veteran like Levi Wallace, who can play multiple spots in the secondary. In Week 5, Wallace gave up two catches for 14 yards on three targets in 24 coverage snaps, according to Next Gen Stats. He played a total of 42 defensive snaps and could see his playing time increase on Sunday.

“Levi is a must-have for us,” Joseph said. “(He’s) a veteran player (who) can play safety, nickel or (outside) corner for us. He can fix issues on game day.”

Fortunately for the Broncos, they will face a Saints team that could be without their top two wide receivers. Chris Olave (concussion) and Rashid Shaheed (knee) were listed as non-participants at practice for two straight days.

Meanwhile, backup quarterback Spencer Rattler will make his second career start since starter Derek Carr is sidelined with an oblique injury.

“It takes some adjusting in the back end to fit certain packages (for) certain players,” Joseph said. “We should be OK.”

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