Quick Hitter: New Rules for 2020

As I understand it, there is no limit to how many players you have in the dugout, just how many are available to be used.  For example, when a player gets hurt, he is free to sit in the dugout during the game even if he is on the IL.  If indeed in September you can change your 28-man roster without needing to option players, the 12 players not on the "active roster" will likely just sit in the bullpen/dugout.  As other posters have pointed out, if this is the case, all 4 starters not scheduled that day will be deactivated, meaning it's not really a 28 man active roster, it is a 32 man roster (with only 1 starter active, each team can have a mix of 27 relievers/position players).

There is no limit to how many people you have in the dugout, but as you note there is a limit to the active roster size. And in order to have a "daily active 28" in September from among the whole 40-man roster, you'd need a pretty big change to the rules -- allowing teams to call up players, but not put them on the active roster. That's not currently allowed, and it could affect options, service time, benefits, postseason eligibility, etc.

I'm not so sure that's part of the deal here, but official details have been scant so far.

Great rule change on upping the number of batters to 3. That in fact will certainly improve pace of play more than anything that's been done so far.

Well, just about anything could improve the pace more than the pointless "mound visit limits" or "automatic intentional walks", so that's a pretty low bar.

Do we have any numbers on which teams used relievers the most for less than three batters and didn't finish the inning?

I haven't seen a team breakdown, but this article listed some league-wide numbers:

https://www.mlb.com/news/how-3-batter-minimum-will-change-baseball

 

 

How much will this actually change things?

We need to split this up into "relief appearances of zero, one, or two batters where the inning is ended," thus freeing the reliever from the requirement to stay in, and "where the inning is not ended," because that's now important. If we look back at the last 20 seasons, we can see that the number of relief appearances that don't stretch to three batters has increased markedly ... but the number of appearances where a pitcher did that and didn't get to the end of the inning hasn't.

Basically, we're looking at about 800 or so of these soon-to-be-banned relief appearances each year, plus a small impact to the length of "opener" appearances, because we're looking just at relievers for this data. While that hasn't changed appreciably over time, it's still notable. There are 26 weeks in a Major League Baseball season, and we saw 779 of these appearances in 2018. That's about 28 times per week, or roughly one per team per week.

(emphasis mine)

In terms of pace / time of game, I think this is closer in effect to the automatic intentional walk and mound visit limits than people think. MLB has yet to address the elephant in the room, which is all of the extra idle time between pitches.