No, 14.5% is not close to 15.5%
Of course it is, especially with something like HR/FB. A difference of 1 HR every 100 FB is extremely close. There is no way you can say that multiple guys maintain a 14.5% but 15.5% is so absurdly high that nobody can sustain it.
But look I have 4 categories of pitchers myself.
1. Every day starters. These are guys that I will start in almost every matchup all year long. Sure I might sit Gallardo against STL and @Col but he is still an everyday starter. There are only like 30-40 of these in baseball.
2. Situational starter. These are guys that I don't want to drop ever, but I will start or sit them based on matchups. Guys like Lincecum, Morrow etc. Basically guys I have enough doubts about that I don't want to also have a bad matchup. In a league with no bench these guys slide up into the every day slot because you have no choice. In a weekly H2H league these are the guys I swap around on 2 start weeks. This is where I would probably put Cashner. This list goes a lot deeper depending on the league but probably like the top 75 or 80.
3. Spot Starter. Guys I will pick up for a matchup play and then as soon as there is a bad matchup I will just drop them because it won't bother me if someone else picks them up. These are safe low upside guys (usually low K) like Detwiler and high upside high risk guys like say Peralta and guys who excel at home etc. If Cashner gets off to a bad start this is where I will slot him, I won't spend a long time keeping him in #2.
4. Not worth anything. This is the rest of the starters that I feel are just too risky or a combination of risky and mediocre that even with a good matchup I don't really want to start. These guys can move into #3 on a temp basis if they are hot.