ATHENS — Detroit Lions quarterback Matthew Stafford was back on the University of Georgia campus on Friday to speak to high school coaches about red-zone offense. Beforehand, he sat down with local reporters, who asked what his message would be on the subject.

“I’m going to tell them just to throw it to Calvin every time,” Stafford quipped. “That usually works out.”

Well, it used to work.

Calvin Johnson, the NFL superstar receiver known as “Megatron,” shocked the world in late January when he decided to retire from professional football. The former Georgia Tech standout is 30 years old.

But Stafford said he was not among those shocked by the news. He saw it coming.

“Not to say that I expected it, but I wasn’t shocked,” Stafford said. “I’ve known Calvin for seven years and, you know, I know the effort and the attitude that he plays with takes a toll on people. He was catching quite a few passes and getting hit quite a bunch. It takes a toll. He’s a guy from an offensive standpoint who was touching the ball or carrying the ball as much as anybody. So I knew the NFL was kind of wearing on him.”

In 2012, broke Jerry Rice’s NFL single-season record for receiving yards, which had previously been 1,848, and with 1,964 yards. Johnson caught 731 passes in nine seasons, setting Lions’ franchise records with 11,619 yards and 83 touchdowns and setting NFL marks for consecutive 100-yards games (8) and being the fastest player to 10,000 and 11,000 career receiving yards.

At the rate he and Stafford were hooking up, surely numerous other records would have fallen. But Stafford said he and Johnson are both at peace with Johnson’s decision to walk away.

“I just told him when he told me he was done, ‘I’m happy for you if you’re happy. That’s what you want,'” Stafford said. “He’s a guy who gave everything to the game. You want him to be able to walk out on his own terms and feel like he did the right thing.”

That’s all well and good, but Stafford is not going anywhere. And his has been a long and arduous road with the Lions, who drafted him with the No. 1 overall pick in 2009. The franchise has yet to make the return to glory it envisioned when it brought together Stafford and Johnson.

Now Stafford must carry on without his primary target for the last seven years.

“It’ll look different, obviously,” Stafford said. “He was a player who drew a bunch of attention not only in the red zone but all over the field. He’s a guy that led that receiver group. He showed those guys what it was like to work and what it was like to try to dominate a game, to take over a game. We’ve obviously replaced with some pieces. No one player is going to replace a guy like that. But I’m confident in our coaches and the players we have on our team. We’re going to be fine. But you’re going to miss a guy like that. He makes plays that one, two, maybe three guys can make and he was doing it on a consistent basis for a long time. So it will be difficult to start, but we’ll find a way to still be explosive, still score touchdowns and do all that kind of stuff.”

With or without Johnson, Stafford is in it for the long haul with Lions. He signed a three-year, $53 million contract extension in 2013 that will keep him in Detroit through the 2017 season.

He is somewhat of a polarizing figure in that city. In a lot of ways he was considered the town’s football savior when the Lions made him the No. 1 pick in the 2009 draft. But Johnson’s sudden retirement is one of many changes both Stafford and Detroit’s football fans have had to endure.

“For me, and throughout the seven years I’ve been in the NFL, my biggest takeaway was just control what you can control, because there are a lot of variables out there that you can’t,” Stafford said. “People are going to like you or they’re going to dislike you for whatever reason. I wore my hat forward today so people like me. If I wear it backward people don’t. I’m not a novice anymore. Little things you can’t control, but you just try to go be yourself to be the best player you can possibly be. You do that and the rest will take care of itself.”

Stafford, who maintains an off-season home in Atlanta with his wife Kelly, said retirement hasn’t entered his mind at all.

“No, I still love it,” he said. “Some people think it’s less fun, but I love it. I enjoy playing the game, I enjoy the preparation, the hard work that goes into it, the teammates, the camaraderie. Winning is obviously a lot of fun. But it’s different, no question. People come and go at way more of a rapid pace.

“I remember my rookie year, we had just come off the 0-16 season and we didn’t play so hot. It felt like I had three new teammates every week. We were shuffling guys in trying to find the right guy who could help us. It was a unique experience and it was a rude awakening to the business of the NFL. If you don’t win bad things happen and if you do win good things happen. That’s not only on the field but throughout the organization. It’s a tough deal, it’s tough business. But I personally wouldn’t trade it for anything.”