You don't expect your QB to hold onto the football? Pretty low standard.
19-29-181 is not good QB play.
It seems you are using a standard of you can't blame him if you can list some excuses while I am using a standard that I expect my QB to make plays, move the team, put points on the board and overcome mistakes.
Chiefs first half drives:
First drive - 17 plays, ends in WR fumble after 10 yard pass to SD 23 yard line
Second drive - 9 plays, last 3 are pass complete on 1st down followed by 2 runs. FG kicked
Third drive - 1 play kneel down
Chiefs second half drives:
First drive - run for minus 1 yard, 10 yard pass by Cassel, run for no gain
Second drive, post fumrec - Inc on 1st down, 2 runs follow, missed FG
3rd drive - 9 plays starting at KC 7, Cassel brings Chiefs to SD 28, run for minus yards, false start penalty, Inc, completion for 13, FG made
4th drive - starts on KC 8, penalty for false start, 1 yard run, Cassel sacked when Stephenson completely blows his block and hangs Cassel out to dry
5th drive - starts on KC 20, moves to SD 48, then McCluster fails to catch easy pass, resulting in pick 6
Game's over at that point, and the last drive resulted in a garbage TD. Not one KC drive failed because of the QB in the entire game