It seems highly unlikely to me that Mac would spend that kind of cash on a RB. Without a 2nd round pick, free agency becomes that much more critical to fill the many needs of this team. The likeliest scenario is he signs a major upgrade at LT and OLB. Dallas and Detroit currently have $50mm and $39mm of cap space in 2019 respectively. Signing Lawrence or Anseh would cost them upwards of $20mm and that may shake one or both of them loose. Dante Fowler is very likely to be available and provided the Jets are satisfied with their due diligence on him, he could be the guy they go after. It's also likely that Mac will need to sign Carpenters replacement. And a #1 receiver. And another cornerback. Remember, the $90mm in cap space only accounts for Leo Williams, Mike Pennel and the rookie DL. So unless Fatukasi and Sheppard contribute another DL will need to be signed.
Just not a RB.