Andrew Luck = humble, stable, team-oriented professional.
Brandon Marshall = emotionally unstable diva-receiver.
I think it would be a serious culture clash.
Yeah you're right, we probably shouldn't draft Luck when we get the #1 pick. Who would fit in with Marshall the best? We should draft that guy.
Personality clashes can be overcome by a strong winning culture fueled by respected, long-time leaders.
I've seen personality clashes between Tom Brady and Randy Moss, and between Tom Brady and Chad Ochocinco, be won by Brady both times, to the point that Moss and Ochocinco's "diva" ways diminish down to nearly nothing.
What's responsible for that? The Patriots' culture, and Brady's standing as its leader.
Now, I'm not foolish enough to think that a rookie QB can come right in and assume that kind of status, so I'm definitely on board with jettisoning Marshall ASAP, for that reason and others.
Essentially Marshall would need to be cleared out of the way so that Luck, if he's indeed the choice, can come in and develop into the team leader without being impeded by Marshall.
And that development of leadership in the franchise QB is so important that it's worth sacrificing a player with the physical talent of Marshall IMO.
You can always find a physically talented WR later. What you can't do is do over the first few years of development of your franchise QB, the ones that determine his trajectory as the team leader.