ALLEN PARK -- Kerryon Johnson is headed for injured reserve with a knee injury for the second time in as many years, dealing a major blow to Detroit’s running game and sparking more questions about his long-term health and durability with the team.

Johnson injured his right knee during Sunday’s loss against Minnesota and underwent a procedure early Tuesday. He is eligible to return for a Week 15 game against the Tampa Bay Buccaneers, so it’s not over for him yet, although the team will exercise great caution in bringing him back from a second major knee injury in as many years.

He missed the final six games last year with another knee injury, cutting short his fabulous rookie season. The second-round pick needed just three games to snap a 100-yard rusher drought that stretched back to 2013, averaged 5.4 yards per carry for the season -- second best in the league -- and looked like he may prove to be one of the steals of that year’s draft.

The Lions were so high on Johnson, they fired offensive coordinator Jim Bob Cooter and replaced him with a playcaller in Darrell Bevell who had installed some terrific running systems in Seattle and Minnesota before that. The idea was to re-orient the offense around Johnson, which would bring better balance to the offense and take some of the pressure off Matthew Stafford.

There was hope Detroit could maybe field its first top-10 rushing attack since the days of Barry Sanders. Yes, it has been that long, 1998 to be exact.

But while Johnson has been featured more prominently this year, the results simply haven’t followed. He’s averaging just 3.3 yards per carry -- more than 2 yards fewer than last year every time he touches the ball -- and also struggled with ball security, including fumbling at the goal line in a critical sequence against Kansas City, then dropping a third-down catch that would have given Detroit a critical first down late against Green Bay.

The Lions are averaging 103.2 rushing yards per game as a team (18th in the league), and just 3.8 yards per carry (23rd).

Part of the struggles are the result of all the loaded boxes they have faced -- more than just about every team in the league -- but Johnson had his share of issues too.

"I’ve got (my own mistakes) in there,” Johnson said last week. “The thing about me, I’m not afraid to admit that. I’ll tell them that, I’ll tell you that, I tell my teammates that. If I mess up, especially Arizona -- there were three runs I messed up. (In Green Bay), there were two I messed up. I can’t make a perfect read every time. But I try my best, and as long as you’re up front about that, it’s something your teammates can trust you on.”

Johnson struggled again last week against Minnesota, though, before leaving the game after five carries with another knee injury. He returned to the sideline with a brace. And now there’s no telling when we’ll see him again, sparking real questions about just how much the Lions can trust him going forward, considering the injury issues that began at Auburn and have now followed him to Detroit.

Now the focus turns to rookie Ty Johnson, plus recent pickups like J.D. McKissic and Tra Carson. Those guys combine for 192 rushing yards on 38 carries and no touchdowns this season.

Johnson finishes the year with 92 carries for 308 yards and two touchdowns.