The Chiefs are at a critical juncture. They have most of the pieces in place to be contenders for the next few years, but if they don't make the right offseason moves, that opportunity could be missed. On offense, they could use a new quarterback, but it's not close to their most pressing need on that side of the ball. The offensive line needs improvement. While the quarterback may be the most important position on the field, it isn't more important than the entire O-line. If the O-line isn't addressed, it won't matter who Pioli might be able bring in as quarterback, he won't be able to perform to his full potential. The O-line should be the number one priority of the draft.
If the offensive line sees significant upgrades via the draft, I think Matt Cassel has what it takes to be an above average performer next season, though I doubt that he's ever going to be a top-tier quarterback. Still, the Chiefs can win with Cassel. It wouldn't be ideal, but it wouldn't be the end of the world, either.
For two consecutive seasons the Chiefs have found that their backup quarterback has not been up to the task. Given that Stanzi didn't get a chance to play last season after Cassel was injured and Palko struggled mightily, I have my doubts that he is developing as the coaching staff had originally hoped. So, either the Chiefs need a new starting quarterback, displacing Cassel to second string, or Cassel needs a new backup.
The cap space is there to address the QB position in free agency. The choices aren't plentiful this year, but options do exist. Brees, Manning, Orton, Campbell, and Flynn are all legitimate possibilities.
Bringing in Manning is a bad idea. He's a high risk choice with limited payoff potential. Best case is KC gets about three good years out of him. In all likelihood, his best years are behind him, so the Chiefs probably would not see elite performance. Worst case, he is no longer up to the task of starting quarterback in the NFL, unable to sufficiently recover from injury. No matter what, he offers no hope of being the quarterback of the future.
Brees would not be a bad choice, but still not a great one. He would be expensive, considering he's likely to be tagged (if not resigned). But, going into his eleventh NFL season, like Manning, he's not the quarterback of the future. He does probably have a few more seasons in him than Manning though.
Both Orton and Campbell are safe choices. Neither one is terrible, but neither one is great, either. It's not a foregone conclusion that either one could beat Cassel in the competition to start. That's not necessarily a bad thing. Cassel plus either one of them would be a better number one and number two than the team have right now, no matter who starts. Like most low-risk choices, the downside is acceptable, but the upside isn't substantial.
Flynn is the best option. Like Manning, he's a high risk choice, but he offers the greatest potential for that risk to pay off big, and the potential downside is more acceptable. It's true that there isn't much game performance with which to analyze Flynn. That should also help keep him from being cost prohibitive. And when he has played, he has played well, including breaking a couple single game franchise records in Green Bay. Chances are very good that he could handily beat Cassel for the starting position. He's also young enough to be the quarterback of the future in Kansas City. There is always the chance that Matt Flynn is Matt Cassel 2.0. If that's the case, then, with respect to performance, it's no worse than bringing in Orton or Campbell. It's just more expensive. With the Chiefs' cap space, that's a risk the team can afford.