There was a long form article on ESPN during spring training last year that also reported deGrom was planning on intentionally taking some velo off his fastball in order to stay healthy.
It was apparent on a pitch-to-pitch basis when watching his starts. He was consistently 96-98. He would only very occasionally reach triple digits, exclusively in the biggest circumstances.
That's fine to do, and it helped him stay as healthy as he's been in a while. Now, he just has to realize you have to mix in offspeed pitches more, specifically his changeup, to keep batters on their heels a little. Gotta keep them thinking about something other than the heater when you aren't throwing it triple digits with insane spin rates anymore.