Before they were beheading Life Model Decoys, Marvel's Agents of S.H.I.E.L.D. were busy having a run-in with the vengeful Ghost Rider, Robbie Reyes (Gabriel Luna). Earlier in the season, we got to see the show's take on Robbie's origin story and how he became united with the Spirit of Vengeance. Fans were elated when it was revealed that a second Ghost Rider (implied but never confirmed to be Johnny Blaze) passed the spirit into Robbie, saving his life. 

Many people hoped that this small cameo was hinting at things to come; in the comics, Blaze was a mentor to Robbie, helping him understand what he had become. With Blaze seemingly appearing on Agents of S.H.I.E.L.D., some hoped we'd be seeing a team-up between the two Ghost Riders in a future episode, or a spin-off show focusing solely on them. Sadly, producer Jeff Bell has cleared the air on the subject which douses the chance of audiences ever seeing the two Riders unite.

According to Bell,
Source: COMIC BOOK MOVIES