We’ve long treated The Athletic’s MLB mailbag the way managers once treated starting pitchers: give someone the ball and see if they can go the distance.This time, we’re experimenting with a different approach.It’s a mailbag bullpen game, and while I have the ball here in the top of the first, I’m more of an opener. My job is to give the team one good inning before a bunch of relievers come out of the bullpen, one after another — and we’re playing matchups. Specific writers are going to respond to specific questions based on expertise and experience. As always, some questions have been edited for clarity.I’ll start us off.Can someone explain the difference between the IL stints? Is there really a difference between IL10, IL15, and IL60? — Tom R. Under the current system, the 10-day IL is for hitters, and the 15-day IL is for pitchers (and two-way players). The numbers mean what you think they mean: A player on the 10-day IL has to be on the injured list for at least 10 days, and a player on the 15-day is out for at least 15 days. An IL stint can be longer but not shorter.The 60-day IL is for long-term injuries, and the designation matters because players on the 60-day do not count against 40-man roster limits. So, if a team needs to open a 40-man spot, it can do so by moving a player to the 60-day IL, but that player has to miss at least 60 days (if a player has been on the 15-day IL for 20 days, then goes on the 60-day, he only has to miss 40 more days).To make sure I wasn’t missing anything, I texted a longtime executive:“That pretty much covers it,” he said. “There’s also a 7-day concussion IL. Also, there is some nuance to the 60-day IL, but that detail may be unnecessary.”— Chad JenningsWhat are the most likely rule changes in the next 1, 3, 5 years?? — Eric R.First guy out of the pen is our resident Hall of Famer, Jayson Stark. Jayson, take it away: With labor Armageddon hovering, it’s unlikely you’ll see anything new next year. You could see tweaks to ABS, but that wouldn’t qualify as a rule “change” in my dictionary. But once the labor clouds lift? Then the league could start implementing — and experimenting with — more impactful and creative rule changes. Such as: