Shaq's playing time in Miami is dwindling aka he's not a full time starter as he's gone from 94% of their defensive snaps in the 1st week to 41% in their Week 9 game, Week 10 stats aren't up yet. https://www.pro-football-reference.com/players/L/LawsSh00.htm
If Johnson was better he'd be getting more snaps, Espenesa getting hurt didn't help his cause yesterday.