Calvin Johnson's relationship with the Lions has been rocky ever since he retired a year ago. But the Lions appear to be taking a step toward mending their broken relationship. 

On Monday, Lions president Rod Wood told WJR Radio that the team invited Johnson to training camp. 

ESPN's Michael Rothstein has more:

"I did invite him out to training camp," Wood said on WJR on Monday. "We'll see if he does that. Hopefully he shows up and he's a great player. We want to have him in the tent and not outside the tent."

Wood said Johnson's displeasure with the Lions is "a little disappointing," but he concurs with what Caldwell said during spring workouts that they hope they can work things out with the former star receiver. Wood said he's exchanged text messages with Johnson in recent weeks and they have been "very cordial" and "very professional," but he declined to get into specifics.

The public rift between Megatron and the Lions peaked recently when the former receiver said in May that the team mistreated him on his way out.

"I don't even like to talk Lions too much just because the way our relationship ended," Johnson told the Detroit Free Press at the time. "If they see me around here, we'll see. But hey, I don't know.

"I just didn't feel like I was treated the way I should have been treated on the way out. That's all. I mean, it's all good. I'm not tripping. I don't feel any kind of way, just hey, that's what they did. Hey, it is what it is."

The reason for those comments? As the Free Press reported in June, Johnson paid the Lions at least $1 million when he retired. It was always expected that he'd pay back a portion of his signing bonus, but the figure wasn't expected to be that large. That's likely the reason behind the choppy relationship. Here's where it's worth pointing out that the Lions did something similar to Barry Sanders when he retired.

Johnson hasn't stopped taking shots at the Lions, by the way. Last week, Johnson said he retired because he was "stuck" in Detroit and the Lions didn't have a shot at winning a Super Bowl.

"I didn't see a chance for [the Lions] to win a Super Bowl at the time, and for the work that I was putting in, it wasn't worth my time to keep on beating my head against the wall and not going anywhere," Johnson told FIDAF-TV in Italy.

Previously, Johnson has also framed his decision to retire around his health. In December, Johnson explained that he wouldn't return to football due to health concerns. Still, comeback rumors have persisted due to his age (31). It's not like Johnson retired when he was slumping. In his career, he caught 731 passes for 11,619 yards and 83 touchdowns. From 2007-15, he ranked seventh in receptions, first in receiving yards and first in touchdown catches. In his final season, he caught 88 passes for 1,214 yards and nine touchdowns.

But, about his health ...

"I'm not coming back, man," Johnson told ESPN in December. "Look, man. I got stuff that's going to hurt for the rest of my life. I got a finger that's literally bone-on-bone. This bad boy, it gets smaller. The more and more I do, it grinds bone-on-bone.

"Literally from last year, I went this year to get another X-ray and this is after I retired, I knew it was messed up but I didn't know to what degree because it was hurt."

So, don't expect Johnson to make a surprise return to football, even if he does show up to training camp later this month.