The general consensus for the Arizona Cardinals will be that Kyler Murray, a rookie, will be the defining factor in whether or not the Arizona Cardinals will be good in 2019.
The "X-Factor" question is a bit played out because I think most fans will agree the Cardinals X-Factor is the offensive line.
Yet, if I had to pinpoint one player who will help define the success for the Cardinals in 2019, outside of Murray, it would be Christian Kirk.
Kirk will be asked to take another step in his development and also be someone the Cardinals lean on moving forward. He has to take the next step to make sure that the 2020 NFL isn't about a wide receiver early.
Kirk is the X-Factor for the Cardinals, not necessarily in terms of wins and losses, but in terms of making sure they are building well through the draft and the future is bright.
Who is your X-Factor?