Matthew Stafford started 16 games in 2018. It was the eighth straight season he had done so but it was the first time he had thrown for fewer than 4,000 yards. And his 21 touchdowns was his second-lowest total during that stretch (he had 20 in 2012). Advanced metrics painted a similar picture; Stafford ranked 20th in total value and 21st in value per play among all quarterbacks, according to Football Outsiders.

We may now have a reasonable explanation as to why: "He had a broken back last year," Mike O'Hara, who writes for the Lions' team site, said during a recent episode of his podcast with WJR's Ken Brown (via MLive.com). "Broken bones in his back."

NFL.com's Ian Rapoport described the injury as "tiny fractures in his back."

Stafford was listed as questionable in Weeks 14-16 but started all three games, as well as the regular-season finale. Over that stretch, the Lions went 2-2 and Stafford threw three touchdowns with no interceptions.

The 2009 first overall pick has four years left on a five-year, $135 million contract he signed before the 2017 season, and the Lions have shown no signs of wanting to move on from the 31-year-old.

"[Stafford] had the back thing, and he went through numerous things where he wanted to play through it and our doctors said he could play through it," general manager Bob Quinn said in January, via MLive.com. "He showed a lot of toughness. That's a credit to him. That's one thing I'll never, ever question. This guy loves football, he's competitive, he's talented. We need to do a better job of putting better players around him and scheming up things better to use his talent."

New offensive coordinator Darrell Bevell is installing a new scheme, one that should make life easier for Stafford by focusing more on the rushing attack, which he had a lot of success running in Seattle.

"I'm just excited about working with him and just improving some of the little things I'd like to improve," Bevell said last month, via the team's website. "And then ask him to do a few things he hasn't done a lot of.

"We're not going to ask him to do things he doesn't do well. We want him to be able to do things that he does well and feels comfortable doing, but there might be some things he can do well that he just hasn't done, so he's not comfortable with doing it just yet, and I think those are the things we want to push him on."

Meanwhile, running back Kerryon Johnson, the team's 2018 second-round pick who averaged 5.4 yards per carry as a rookie, also expects to benefit from playing in Bevell's offense. He had to look no further than the success Marshawn Lynch had with the Seahawks.

"Yeah, that's obviously good news for me, but we're a complete team," Johnson said in early May, via ESPN.com's Michael Rothstein. "We're trying to be a complete team. We're trying to be a complete offense. We're trying to be complete players, so we understand you can't run the ball 100 percent of the time and you can't throw the ball 100 percent of the time. We just want to be as balanced as possible and score as many points."

And that starts with making sure Stafford is completely healthy.