ALLEN PARK -- C.J. Anderson was signed to be the veteran complement to Kerryon Johnson, and three days into training camp, there’s no reason to think he can’t win the job.

But don’t count out Zach Zenner quite yet.

If Zenner’s career has taught us anything, it is to never count him out.

He joined the Lions as an undrafted rookie out of South Dakota State in 2015. The odds are always long for UDFAs, no matter how good they are, but Zenner was really good. He led the NFL in rushing that preseason, and wound up squeezing onto the roster behind Ameer Abdullah, Theo Riddick and Joique Bell.

Four years later, he’s outlasted them all.

Zenner has been hurt over the years. He’s broken his ribs. He’s been hospitalized with a collapsed lung. He’s broken his back. Last year, he was even cut.

But it’s 2019, and he’s still standing.

In fact, you could argue Zenner is better than ever. When he broke his back in last year’s preseason finale, he thought his career might be over. His subsequent release seemed to only confirm those fears. But he wasn’t ready to give up on football, and enlisted the help of Michigan Elite Conditioning For Athletes in Novi to put him through some of the most rigorous conditioning of his career.

It worked. He added 14 pounds of muscle while trimming his body fat from 12.6 to 8 percent. That’s hard to do, in case you were wondering. And when the Lions called him looking for running back help in the middle of the season, he rejoined the team in tip-top shape.

Zenner rode the bench for a few weeks. Then Kerryon Johnson suffered a knee injury, and Zenner suddenly found himself in a backup role. Then LeGarrette Blount floundered ahead of him, and just like that, Zenner had gone from his couch to the starting lineup in a matter of weeks.

And he excelled in the role, averaging 4.8 yards on his 55 carries. That was better than any back not named Kerryon Johnson in Detroit, and would have ranked 15th in the league if he had enough touches to qualify.

Nobody is saying Zenner is the 15th-best back in the league or anything, but he was clearly better than Blount -- yet another back he’s outlasted in Detroit -- and now heads into 2019 even bigger than ever.

Zenner said he’s checking in at between 220 and 225 pounds, the biggest he’s ever reported for camp.

“Put on a little bit more weight," Zenner said after practice on Saturday. "Continued to train out in Novi. Got a lot of good training out there this summer, which was really good.

“(Getting bigger) just sort of happened with the training. And if you can stay lean and fast, bigger is better.”

Make no mistake, Zenner appears to still be moving well. He looked good in an expanded role Saturday, too. With Kerryon Johnson not practicing because of an unknown reason and Theo Riddick getting cut shortly before the workout, Anderson and Zenner operated as Detroit’s top backs, ahead of Mark Thompson, rookie Ty Johnson and fullback Nick Bawden.

Zenner drew cheers from the fans on one carry where he zipped untouched through the first two levels of the defense, and later rumbled into the end zone for a touchdown during fourth-and-short drills from the goal line.

Of course, Anderson also scored on the previous play. Anderson has more experience than Zenner, too, and way more production, including a 1,000-yard season for Denver just two years ago. He’s appeared in multiple Super Bowls, including just last year, when he replaced Todd Gurley for the Rams down the stretch.

So, yeah, Anderson has a really good chance of winning the No. 2 job.

But Zenner should be in play too. The Lions also are installing a new offense that is expected to lean on the running game more heavily. That means they need bodies. Kerryon Johnson will lead the rotation, no doubt about that, but Detroit needs reliable options behind him to share the load when they’re at full strength, and step in when injuries hit.

And time and again, Zenner has shown you can’t count him out.