Withey's improve was under Manning. Ellis was with Manning as well for a while. What has Lucas improved at? He is a good rebounder and defender that's it, his offense is bad. Rebounding and defense at this level is more about desire and drive than coaching. Sure there's things coaches can teach but if the player doesn't have the desire to do those things it's pointless. Embiid maybe
Ellis was with Manning one year. Withey was a transfer and Withey made a huge jump the year after Manning left.
Lucas has become a dominant rebounder and his offense has been getting better.