It wasn’t supposed to be this way.

Adding Kelvin Benjamin to an offense that led the NFL in scoring a year ago was, according to Panthers general manager Dave Gettleman, “like getting an extra first-round draft pick.”

But as a lost season winds down in Carolina, questions linger about Benjamin’s true value. And it’s not just a matter of his 6-foot-5 talent.

“He’s like a lot of young guys,” offensive coordinator Mike Shula said Monday. “When things don’t quite the way you want them to, you get frustrated. Sometimes we can all handle that better.”

For most who watched the Panthers hang on to beat the Chargers Sunday, it appeared obvious Benjamin didn’t deal well with frustration. He was twice bailed out when replays reversed what would have been a total of 142 interception return yards by defenders he failed to make sure were down before the whistle.

But when reporters asked about Benjamin afterward, coach Ron Rivera said, “I’m not sure what you are trying to create.”

Perhaps Rivera really didn’t see anything wrong or maybe he was protecting a guy who’s heard concerns about effort since his days at Florida State. Shula, at least, acknowledged Benjamin might not be as mature as some 25-year-old wideouts.

“He’s still learning about all aspects of the game — the mental part, the physical part,” Shula said. “He’s still young. He’s had one year and missed last year.

“Tell you what — he’s a warrior because he’s been battling some injuries and he’s fought through it.”

After Benjamin had landed on his shoulder while trying to make a catch against the Saints in Week 11, his playing time took a dip during the Panthers’ two-game West Coast swing. But against the Chargers, he was back up to 50-plus snaps, yet finished with one catch for 11 yards.

Through 13 games, Benjamin’s caught 51 passes for 765 yards and five touchdowns. It’s not an exceptionally steep fall from his rookie season, but it’s off pace from his 73/1,008/9 line that year.

And somehow, adding a 2014 first-round pick back into the mix has equaled a year-over-year drop from 1st in points and 11th in total yards to 13th and 19th respectively as of Monday afternoon.

“We’ve all wanted to be better than where we are,” Shula said. “But we felt going into this season he’s just another piece that’s been added.

“Is he going to be one of our go-to guys? Yeah, for sure. But he’s not our only one.”

For what it’s worth, Benjamin’s five touchdown catches are a team high. But only two of those have come after he looked like the guy he was expected to be in the first two weeks of the season.

Against Denver and San Francisco, he totaled 13 receptions for 199 yards and three scores. In the 11 games since, he’s caught just 38 balls for 566 yards.

If Sunday happened in a bubble, Rivera’s terse defense of Benjamin might have been understandable. But before that, his season featured some of the more infamous moments of a forgettable year: A touchdown-negating block in the back against the Vikings, a game-changing fumble versus Kansas City and a sideline outburst in Oakland.

Then came the Chargers win which could’ve gone the other way if not for replay.

“We talk to all our guys about playing to the end of the whistle,” Shula said.

OK, but were you upset your best receiver didn’t on multiple occasions?

“If we talk to all our guys about playing to the end of the whistle,” Shula said, “and the whistle hasn’t blown, and they haven’t played till the end of the whistle, then we’ll remind them.”

And as it’s becoming clear, don’t expect the Panthers to blow the whistle on Benjamin anytime soon.