ALLEN PARK, Mich. -- Kerryon Johnson knew all about Bo Scarbrough well before the free-agent running back ever ended up with the Detroit Lions in November.

Like many football aficionados -- Johnson was familiar with Scarbrough for a long time, as far back as when Johnson was in high school in Huntsville, Alabama. There, Johnson, who would sign with Auburn, learned about the legend of Scarbrough from the recruiting circuit, when he was a five-star prospect who landed with the Crimson Tide.

They didn’t really know each other, however, until the Lions signed Scarbrough to the practice squad to eventually help replace the then-injured Johnson in the lineup. From the same part of the country and with an understanding of what it means to play football in Alabama, the two bonded quickly.

With contrasting styles, they might end up being the combination that solves Detroit’s run game in 2020 and beyond. It’s a duo both are comfortable with. They know they have different styles -- Scarbrough is a big, power back while Johnson is a smaller, shiftier runner.

“It makes a huge difference,” Johnson said of having another back to share the workload. “Any running back will tell you, every running back wants to be that guy, but in terms of longevity, career-wise, longevity of your season, it’s always better. In the grand scheme of things, it’s not going to affect your stats or what you can do.

“It just helps keep you going, years and years, game-after-game. Those days of just one guy, this game is just too physical."

Only eight running backs had 250 or more carries in 2019 and 20 had more than 200. The leader in carries this season, the Tennessee Titans' Derrick Henry, had 303 -- a number not in the top 200 in all-time, single-season carries. Only one rusher since 2010 -- DeMarco Murray with 392 carries in 2014 -- has registered in the top 50 in single-season carries in NFL history.

The construction of backfields has changed, with teams now employing more than one rusher capable of handling a large workload. It keeps them fresh and gives teams options if injuries arise.

It’s why, when the Lions signed Scarbrough and then promoted him to the active roster, Johnson wasn’t worried. He didn’t think Scarbrough was coming for his job. He saw it as a long-term benefit for him.

This past season, Johnson rushed 113 times for 403 yards while Scarbrough had 89 carries for 377 yards. They only played in two games together -- the last two games of the season. Beyond the way they run, the combination of the two can be difficult for defensive coordinators and the front seven players tasked with tackling them.

“It’s hard," Johnson said. "You have to make sure you’re looking out in the game, especially when you start to get tired a little bit and that running back comes in with a full head of steam for three plays and then they put another one in and he comes for it, it’s tiring.

“It’s very tiring for defenses. That’s always a good thing to have.”

The NFL’s No. 1 seeds this year -- Baltimore and San Francisco -- both had diversified rushing attacks. The Ravens used a combination of quarterback Lamar Jackson and rushers Mark Ingram Jr. and Gus Edwards, while the 49ers had a combination of running backs Tevin Coleman, Matt Breida and Raheem Mostert to offer different looks.

Lions head coach Matt Patricia has always wanted this as well, both from his New England pedigree and also in his attempt to keep his backs healthy for a full season. After trying different combinations throughout 2018 and the first half of 2019, it appears he might have found a successful one in Johnson and Scarbrough.

And toward the end of the season, the Lions received a glimpse of their potential future. Johnson came back from injury in Week 16 against Denver, and the duo combined for 76 yards against the Broncos and 95 yards in the season finale against the Packers. It might not sound like a lot of yardage, but both averaged over four yards per carry over the last two weeks, too -- perhaps a better barometer for effectiveness.

“It just balances us out,” Scarbrough said. “You have two different types of runners and the type of receivers we have, it just balances the offense out. If you got a power back and you got a slasher in the backfield, it’s different, but it’s also the same, so I think it’s a balance to our offense.”