Well sure if you want to count only defacto starters and not guys who have shown they are starting calibre running backs in multi back schemes.
Nyheim Hines
Philip Lindsay
Tony Pollard
Tariq Cohen
Jamaal Williams
Wayne Gallman
Marlon Mack
Jordan Howard
Tevin Coleman
Mike Davis
Jay Ajayi
Jerrick McKinnon
Etc etc
I don't think the Cards are looking for a bell cow back again. I think they learned that lesson. And there's no super star elite running back in this class IMO.
I think they take a cheap vet like Duke Johnson or Tevin Coleman and maybe add a lower round project.
You're really stretching "starting caliber" here.
Nyheim Hines - Zero 100 yard games in 3 years. Decent receiving back, not a full time starter. Won't be in 2021.
Phillip Lindsay - Maybe, but also if he's so good, why pay Melvin Gordon? Probably not a starter in 2021.
Tony Pollard - Two 100 yard games. Was pathetically ineffective in two starts last year. Not a starter in 2021.
Tarik Cohen - Zero 100 yard games in 4 years. A good returner and receiver, not a full time starter. Won't be in 2021.
Jamaal Williams - Two 100 yard games in 4 years. The team drafted an RB in the 2nd round last year so he might not even be back in 2021, much less a starter.
Wayne Gallman - One 100 yard game in 4 years. This guy was the definition of pedestrian all year despite having almost all year without Saquon to show something. Won't be a starter in 2021.
Marlon Mack - I'll at least give you this one, but the guy's goose is probably cooked after an Achilles tear.
Jordan Howard - He deserves some credit too, but got traded for a song and hasn't done much of anything since his first two years. Might not even make a roster in 2021.
Tevin Coleman - He was drafted in the third round, so doesn't count.
Mike Davis - One 100 yard game in 5 years, 4 different teams, 5 if you consider his two stints with Carolina. Don't let that serviceable fantasy streak fool you.
Jay Ajayi - One good year, then fell off a cliff and didn't even make a practice squad roster in 2020 with all of the space in the world for teams to add him.
Jerick McKinnon - Third round again, doesn't count. Even then, the guy has one 100 yard game in 6 years.
For the most part, outside of very unsustained stretches, all of these guys have been complementary players. Sure, some teams can find a way with a committee approach, but it's telling that almost every single one of these guys either had a higher drafted replacement, were traded away, cut multiple times, or lost their job to someone else.