On teams I follow, it generally seems that there is more than one reliever who is getting almost no work. Those mop up innings could go to the 6th reliever instead of the 7th. Since the 6th reliever isn’t pitching too many times a week anyway,.

*If you had a terrific pinch-runner – a guy who could steal practically at will with an 85% success rate, and he did nothing else for your team…how much would he be worth over the course of a season? One win? 1.5? Enough to justify carrying one all year?

*How many at-bats does a player need, on average, per week in order to remain alert and effective? This is surely a consideration for the teams that opt to carry four-man benches in the AL. Pinch-hitting opportunities are almost nil; if your 5th bench guy was only going to get a start every two weeks, he’d probably be terrible in the role anyway, because he’s so rusty when he finally plays.

*When we’re talking about only four precious bench spots for AL teams, it strikes me that “backup catcher” ends up being a roster slot that produces very little value. Thinking about alternatives: When was the last time a team carried a backup catcher with true versatility? Like, if Jake Fox were to be the A’s backup catcher for 2010, or if Pablo Sandoval was the Giants backup catcher entering last season, Brandon Inge, etc. A guy who hits or fields well enough to justify playing him signficantly at another position also moonlights as your 30-games-a-year, once-a-week backup catcher. Does this ever happen anymore? If not, is it because catcher defense is too important and difficult to entrust it in the hands of someone who is also putting in a lot of work at 3b/1b? If teams could get away with not carrying a light-hitting backup exclusively devoted to playing catcher, it would free up an additional roster slot for platooning.

AND…who won’t bitch excessively about being a part-time player. I think a small, small additonal factor in the shift to 7-man bullpens is that a hypothetical “5th/6th bench guy” really wouldn’t play that much, and that most players do not prefer to be a part of a platoon. Many who are put in that role complain about it. Everyone who is physically capable would prefer to play everyday rather than be a platoon guy, even if someone pointed out their bad splits to them.

That issue of being underused and the locker room problems it could create doesn’t exist as much with relievers. They are used to spending a lot of their baseball life just watching the action. Plus, it’s easier to use a 7th reliever to his full physical capability – to make him feel “useful” – you’ve only to pitch him a few innings a week to do that.

I have no idea if any of it helps.