The Sun says Hull are ready to go back to the FA again over the tackle by Newcastle's Guthrie which broke Fagan's right leg.
Guthrie was sent off after a shocking challenge yet the FA insisted they were unable to extend his automatic three-match ban.
Hull boss Phil Brown said: "I was disappointed by the FA response. They just said they couldn't do anything more but it seems that they can.
"This was a callous, cowardly, vicious attack."