The Patriots could not keep two quarterbacks on their roster that took up $29.2 million of salary cap space, so it wasn't a matter of if the Patriots would trade Matt Cassel, but when.
The Chiefs, with former Patriots vice president of player personnel Scott Pioli in his first year as general manager, were the perfect fit.
The first step was Pioli going through a thorough analysis on his incumbent quarterback, Tyler Thigpen. Pioli learned a great deal of football from Bill Belichick, and one of the things Belichick always says about quarterbacks is that nothing is more important that decision-making and accuracy. Thigpen's 54.8 completion percentage in 11 starts last season probably gave Pioli pause.
The other factor in play with Cassel was determining what type of market would exist for him.
Part of what made his situation so compelling is that there are only 32 starting quarterback spots in the NFL, and many of those spots were already filled. Add in the finances and draft-pick compensation involved, and the projected field figured to be narrow from the start.
In the end -- when factoring in the combination of quarterback need and market conditions -- the Chiefs turned out to be one of the only horses in the race.
(more analysis to come when trade compensation is confirmed)