– Long after Friday morning’s practice, after most of the players were gone, Adam Thielen and a few other receivers were standing a few feet in front of a JUGS gun that was spewing footballs hard and fast. From one side and the other. With his left hand, and then the right, Thielen practiced.

Then: autographs, smiling for pictures with a few fans wearing his No. 19 Vikings jersey and facing the question he gets more than a few times a year:

What’s it like sitting, precariously, on the bubble, again?

That’s Thielen’s reality. The former Minnesota State Mankato star receiver was an undrafted rookie in Vikings camp in 2013. Cut, he was named to the team’s practice squad. A year later, thanks to extensive duty on special teams, he made the roster.

And now all he has to do is do it again.

The addition of Mike Wallace to the receiver corps and the emergence of Charles Johnson last year will make decisions at receiver difficult. Wallace, Johnson and Jarius Wright are locks. The team seems committed to Cordarrelle Patterson, and rookie Stefon Diggs has impressed. If the team decides to break camp with five receivers, Thielen’s chances could get dicey.

That’s why he has the same mentality in this camp that he’s always had. Actually, it’s a fine line. Thielen said he can never forget how precarious his spot on the roster is. At the same time, he can’t let himself dwell on it, either.

“You do that, and it’s going to be tough,” he said. “But you have to treat it like it’s your last day, every day. And just have fun. That’s the biggest thing. If you don’t you’re not going to perform well.”

Thielen played in all 16 games last year, mainly on special teams. He had just eight catches for 137 yards and one TD, a 44-yarder against Chicago.

But he was so valuable on special teams, where he plays on all four units. His first NFL score came against Carolina, last November, when he blocked a punt and returned it 30 yards for a touchdown.

“He did a great job for us last year, and we’re going to rely on him more this year,” special teams coordinator Mike Priefer.

That is, if he again makes the team.

Thielen, who got married in May, spent the summer working out at ETS Sports Performance in Woodbury. He also worked out with Cardinals star receiver — and Minnesota native — Larry Fitzgerald. “You make yourself tougher in the offseason,” Thielen said. “You constantly have to grind, work harder than anyone else.”

Thielen’s work ethic has clearly endeared him to the coaches. Head coach Mike Zimmer talks about him often. Wednesday he raved about Thielen’s catch on a deep sideline route over cornerback Xavier Rhodes. On Tuesday offensive coordinator Norv Turner praised Thielen as well.

“Adam, he is fast,” Turner said of the 6-2, 200-pound Thielen. “He’s got outstanding speed, and he plays extremely fast. … He’s really become an outstanding route runner, and he runs every route full speed.”

Now Thielen just has to prove it, again. He and other players fighting for spots will get plenty of opportunity with the Vikings kicking off a five-game preseason schedule Sunday against Pittsburgh in the Hall of Fame Game.

“I still have a lot to prove,” he said.