I play the matchup, not the opposing pitcher. If the matchup is good, then I start both guys. I look at era/whip/k's. Wins is all run dependant and can't be controlled by my pitcher (s). In your instance, I'd start both guys. Prior is too good to sit, even against St. Luis. Morris against the Cubs could be dicey, but I'd roll the dice and start him as well.
Yes doctor, I am sick.
Sick of those who are spineless.
Sick of those who feel self-entitled.
Sick of those who are hypocrites.
Yes doctor, an army is forming.
Yes doctor, there will be a war.
Yes doctor, there will be blood.....