Both Arizona and Seattle are in position to tailor their offenses accordingly.
Cardinals coach Ken Whisenhunt made allowances for Kurt Warner, who also altered his mindset regarding ball security. Seahawks coach Pete Carroll has sought a run-based offense, but he's a defensive-minded head coach, so his involvement on that side of the ball would be more philosophical.
The Seahawks' offensive coordinator, Darrell Bevell, has worked extensively with Brett Favre in Green Bay and Minnesota, so he has experience with high-profile passers. Bevell is not the headstrong type.
Both the Cardinals and Seahawks have high-profile offensive line coaches who coordinate the running game, same as Manning had with Howard Mudd in Indianapolis.
Seattle has the least to lose among NFC West teams from going after Manning. Arizona would likely have to part with Kevin Kolb after investing heavily in him last year. San Francisco would have to risk the equity coach Jim Harbaugh has built with Alex Smith, all for a player whose health remains in question.