Najee return?

The guys are sensing a Najee Harris return, due to a report from Gerry Dulac. The Steelers may be set to offer the former 1st round pick a 3-year deal worth about $20M. Why? The speculation is that Mike Tomlin wants Harris back, so we will wait to see who wins the power struggle. This would be a big mistake, but what does it say about Jaylen Warren? Could a RB like Nick Chubb be a replacement?