Adam Thielen could have been a Packer.

Scratch that. Adam Thielen should have been drafted by the Packers in the seventh round in 2013 and should still be a Packer to this day.

“I do remember the Packers had interest before the draft,” the Vikings receiver said last week.

They also had three seventh-round picks, two of which they used on receivers. Those receivers caught one ball for the Packers and are long gone from the league.

“The Packers were one of two teams that came up and talked to me right after the regional combine ended at Cowboys Stadium that year,” Thielen said. “I had that hope and dream that I’d get drafted.”

Today, Thielen is a two-time Pro Bowler, a former second-team All-Pro and one of the league’s highest-paid receivers. He’s also a classic example that — sorry, draftniks — the NFL draft never was and never will be an exact science capable of being mastered by bleary-eyed talent evaluators working 23 hours a day.

In 2013, 27 receivers not named Adam Thielen were drafted. Guess how many are now out of the league.

“Close to 20?” Thielen guessed.

Sixteen. Three never played a down. Only two have made a Pro Bowl at receiver.

“Wow,” Thielen said. “That’s crazy.”

Then again, that’s reality, eh Adam?

“It’s a tough league, and you see it every year,” he said. “Just because you’re drafted, No. 1, doesn’t mean you’re going to make a team and, No. 2, it doesn’t mean you’re going to be around a long time. Especially at receiver, where there are only five and the last two have to play a lot of special teams or they’re gone.”

When it comes to the draft, no one has all the answers. Not even an iconic gridiron brainiac named Bill Belichick.

In 2013, the Patriots needed a receiver. They took Aaron Dobson from Marshall in the second round and Josh Boyce from TCU in the fourth round.

Dobson and Boyce spent three years in New England. Both are out of the league. Dobson caught 53 passes in 24 games. Boyce had nine catches in 10 games.

“No one has cornered the market on player evaluation in this league,” Vikings offensive coordinator Kevin Stefanski said. “We do our due diligence. At the end of the day though, no one is going to bat 1.000.”

Of the 10 receivers taken in the sixth and seventh rounds in 2013, nine are out of the league and three never played a down.

The Packers definitely were intrigued by Thielen, the D-II standout from Minnesota State Mankato. Intrigued enough to focus on him at the Dallas regional combine, which Thielen paid his way into because he wasn’t invited to the national one in Indianapolis.

“I was pretty realistic about my chances of being drafted,” Thielen said. “And when the Packers took two receivers in the seventh round, the writing was pretty much on the wall at that point.”

Thielen went his way, parlaying his now-famous rookie minicamp tryout with the Vikings into one of the league’s all-time rags-to-riches stories. Meanwhile, the Packers picked Charles Johnson and Kevin Dorsey 216th and 224th overall, respectively.

Johnson was plucked from Green Bay’s practice squad by Cleveland in 2013. After a three-year stint in Minnesota, he faded from the league. Dorsey played three games for Green Bay, caught one ball and was gone before the 2015 season.

So, what is it that teams miss most often when they whiff on a pick that doesn’t pan out or overlook a player like Thielen?

“I think it really just comes down to whether a guy is a football player,” Thielen said. “And, obviously, that’s a general term and something that’s very hard to judge.”

It’s having the size, speed and athleticism. It’s understanding the game, leverages, game plans. And then keeping the proper passion and work ethic long after the big payday.

“That’s why there is no science to figure who will be successful and who won’t,” Thielen said. “It takes a lot more than seeing a guy run around in shorts and a T-shirt.”

And yet, year after year, the Indianapolis combine creates workout superstars who become all-time first-round busts like Vernon Gholston to the Jets at No. 6 overall in 2008 and Troy Williamson to the Vikings at No. 7 overall in 2005.

Williamson ran a 4.32 in Indy in 2005. Eight years later, Thielen ran 4.49 and 4.45 at Cowboys Stadium. The Packers’ heads were turned. But not quite enough, even on the last day of the draft.

The Vikings are quite happy that no one saw Thielen’s NFL-worthy traits heading into the draft.

“The thing about Adam is his physical gifts are better than you think,” Stefanski said. “He’s bigger than you think. He’s faster than you think. His hands are better than you think. And then when you get him on your team, you find out you couple all of that with a guy who does everything right.”

Former Buccaneers General Manager Mark Dominik says there are two common denominators when it comes to whiffing on a draft pick. One is “falling in love with a guy’s measurables without the production to back them up, and then thinking, ‘Oh, we’ll just coach him up.’ ”

The other is probably the oldest and most accurate cliché used to describe the unpredictability of the NFL draft: You just can’t measure a guy’s heart.

“It’s the one thing there’s really no way of judging,” said Dominik, now an analyst for SiriusXM NFL Radio. “How much do they love the game? How much are they really going to want to work at it, vs. they think they love it and they think they worked at it, but they don’t know until they get to the next level and that’s all you do.

“That’s why I think the draft is so interesting. Because we never know what’s really going to happen.”