Agents of S.H.I.E.L.D. changed things up in Season 4 when it introduced Robbie Reyes as Ghost Rider. The show spent most of the first three seasons pretty firmly rooted in the realm of science, and even the Inhuman legends were based on scientific principles. A man who can light his head on fire because he sold his soul to the devil was something brand new for the agents, and resident genius scientists Fitz and Simmons weren't too happy about it. Actor Iain De Caestecker had this to say about Fitz' feelings toward Ghost Rider:
Fitz and Simmons attack everything from the science point of view and try to find a scientific answer for it. Even though there's this thing in front of him, and there's this story of Robbie being possessed by the devil, it's hard not to have a slight niggling part of his brain going, 'Could this really be magic?' He just doesn't believe in supernatural things, and this is the first introduction of something that's really given him doubts, as to whether or not he could prove the science behind that, or if it's pure supernatural magic.
Fitz has found a scientific basis for even the most fantastical elements of the show, ranging from the variety of powers shown by the Inhumans to Simmons being pulled through a rock to another planet. He could even make sense of how he, Coulson, and Robbie were stuck between dimensions, and he's not always the most patient when he's confronted by something that defies the basic laws of physics and biology. Other agents opened themselves up to the idea of Robbie selling his soul to the devil, but in explaining to Collider why Fitz had problems with the idea that Robbie was resurrected by another Ghost Rider (who may or may not be Johnny Blaze), Iain De Caestecker indicates that Fitz is still very much on the side of science.
Fortunately for Fitz - although not so fortunately for May - the second half of Season 4 is moving focus away from the spiritual and back to the realms of science and engineering. Radcliffe's Life Model Decoy gained awareness after reading from the Darkhold, and A.I.D.A. clearly does not intend to allow humans to control her any longer. She has already built a L.M.D. doppelganger for Agent May, and it looks like she won't keep her agenda a secret for very long in the second half of Season 4. Between A.I.D.A.'s brilliance, her ability to create Life Model Decoy doubles for humans, and the May-bot as an inside source on all things S.H.I.E.L.D., Fitz will probably be so busy trying to use his skills as a scientist to save the day that he won't have time to worry about Ghost Rider.
That said, Ghost Rider didn't actually die when he disappeared in the midseason finale, and executive producer Jeffrey Bell has already said that they deliberately left his fate open. So Ghost Rider could come back at any point in the future, and Fitz will have to deal with him all over again. Tune in to ABC on Tuesdays at 10 p.m. ET to see what's next for Fitz and Co. on Agents of S.H.I.E.L.D., and don't forget to check out our midseason TV premiere schedule.