There are two NFL changes in the 21st Century that continue to surprise: the need teams feel to rush young quarterbacks into the lineup, and the injuries that tear apart most every offensive line during the course of a season.

For decades, even the best of quarterback prospects generally had to be taught the pro game for a couple of seasons before they were anointed as a starter. As recently as 1999, Vikings coach Dennis Green spent the offseason looking for a veteran option before he finally gave the job to Daunte Culpepper, who had played not at all as the No. 11 overall pick in 1998.

Now, we have teams allowing overmatched rookies such as DeShone Kizer and Nathan Peterman to be humiliated by making starts.

The decimation of offensive lines is more startling. The Vikings joined the NFL in 1961, and for decades it seemed that the groups least affected by injuries here and around the league were offensive lines.

The brainiacs in football will tell you the main reason for today’s injuries is that huge offensive linemen are being forced to move more rapidly and at extra distance to block defenders who are faster, stronger and aligned in more exotic schemes.

It is close to impossible to put five competent linemen together and count on them to stay healthy for several years. There are also economics at play, with the value of offensive tackles on the free-agent market.

What any contending team in the NFL comes to appreciate on the offensive line is a reliable utility man, an Eduardo Escobar of football.

The Vikings’ best in this role was Everett Lindsay, a fifth-round draft choice in 1993 from Ole Miss. Lindsay played seven seasons for the Vikings, with 31 starts in 104 games, at both guards and tackles.

The Lindsay types are even more important in this injury-filled era, and the Vikings have one in Jeremiah Sirles, in his fourth NFL season after being signed as an undrafted free agent by San Diego in 2014.

Sirles played at Nebraska and started 41 games in four seasons with the Cornhuskers. “My senior year, we had three tackles, and there were times when I’d play two series at left tackle, then the next two at right tackle,’’ he said. “That was good training.’’

Joe D’Alessandris was the offensive line coach in San Diego. Sirles still makes references to D’Alessandris’ influence, even though he spent most of his one season with the Chargers on the practice squad.

“He had me practicing at all positions,’’ Sirles said. “He said, ‘The more you can do, the longer you stay.’ ”

The Chargers were trying to clear space at the final cutdown in 2015 and traded Sirles to the Vikings for a sixth-round draft choice.

“I got here and the Vikings said, ‘We need depth; you have to be able play anywhere,’ ” Sirles said.

And then this happened: The offensive line of Matt Kalil, Brandon Fusco, Joe Berger, Mike Harris and rookie T.J. Clemmings stayed intact for 16 games.

“No injuries — that was amazing,’’ Sirles said. “Zac Kerin and Austin Shepherd were also healthy, as the sixth and seventh linemen. I was inactive almost every week.’’

That scenario changed dramatically in 2016. “How many left tackles did we have hurt … three, or was it four?’’ Sirles said. “We got wiped out.’’

The injuries also included Andre Smith at right tackle. Sirles started 10 games at that position. He also played two games (one start) at left guard for Alex Boone.

Smith and Boone both left. Riley Reiff (very expensive) came in at left tackle and Mike Remmers (modestly expensive) at right tackle. Rookie Pat Elflein took over at center, with Nick Easton moving to left guard and the versatile Berger to right guard.

“Even with Riley’s sore back in training camp, you knew it was going to be different,’’ Sirles said. “We had a mix of good athletes, strong veterans, and Old Joe the warrior; we all sensed it was a group … that would grow together.’’

This improved offensive line was vital in a 10-2 record and eight-game winning streak. And then came Sunday in Charlotte, N.C.

Elflein and Remmers were out, with Easton at center, Rashod Hill at right tackle and Sirles at left guard. Then, Reiff was hurt, so Hill moved to left tackle, Sirles to right tackle and rookie Danny Isidora entered at left guard.

Last season all over again?

“Just for one afternoon,’’ Sirles said. “We’re good. We’re going to be OK.’’

Having a 6-6, 310-pound 26-year-old who can play both guards and tackles reinforces that idea. And how about center, Jeremiah?

“Let’s hope not,’’ he said. “We’d have to go through Pat, Nick and Joe to get to me.’’