How legit is Devon Achane?

I was pretty ecstatic drafting Achane in the second round last year and he in turn exploded when he was given his opportunity. But how legit is he as a standalone back? What this year taught me (or I at least I like to think so since I ended up trading him away week 4 after the Tua injury) is he may actually just be a system player. He seemed to lack the ability to run between the tackles, lacked that after contact yardage, and seemed like if he wasn't given designed passing plays (with a decent QB), he was pretty much useless. He's also a small dude, susceptible to injuries. I'm internally fighting the regret of trading him away but I was in win now mode at the time and he just wasn't getting it done. My theory at the time was also that Jaylen Wright would be utilized more. Especially between the tackles and in the red zone given his rushing efficiency just seemed to be better. Even when Tua would come back. Whoops. With Tua back, he's back to lighting it up. Is this sustainable? I'm half tempted to pursue Achane in the off-season.