Negatives of the potential move
If Mariota is indeed brought in as a replacement to Carr then it will be a downgrade at the position for the Raiders and that was not the goal coming into the offseason. By nearly any statistical measure, whether it’s accuracy, yards per game, interception rate, or touchdowns per game, Carr outpaces Mariota in every category.
Mariota is just not that prolific of a passer and only has 10 games of 290 passing yards or more in 61 starts, compared to Carr’s 24 in 94 starts. One could say that he is not a pure passer but if you truly want to win you need a QB who can dice up defenses in the pocket no matter how athletic he may be. Even athletic quarterbacks like Russell Wilson or Patrick Mahomes do their most damage from the pocket.
The second possible negative to the signing would be that it could unsettle Carr and shake his confidence if the Raiders bring in someone that he perceives as a threat to his starting role. While there is no reason to believe that this would be the case if Mariota is brought in, then it would be proof that Carr is not a true competitor and would likely spell the end of his career as a Raider.
Again, there is no reason to believe that Carr would be put off by the prospect of competing for his job, but if he is then the Raiders should go ahead and make plans to have someone else under center. By all accounts we know Derek Carr is a competitor and would relish the challenge of keeping Mariota on the bench holding a clipboard and it could inspire him to greater heights.