I was a man on a mission at the GM Meetings Tuesday afternoon in Las Vegas. A question has weighed heavily on me for months, and I needed to get some decent answers to it. I think we all want and deserve an answer, in fact. Most people just don’t know how badly they crave it. What, exactly, is regular rest, anymore? Is it really four days? Do the words ‘regular rest’ mean anything at all?

When I started watching baseball, in 1997, this was also a hot topic, but for a different reason—or, to be more accurate, for almost no reason. That year, it was very clear what constituted ‘regular rest’. The league saw 2,541 starts on four days’ rest, and just 1,021 on five days. Only 150 starts came on three days’ rest, so that practice had nearly gone extinct—but people were talking about reviving it. That’s partially because pitching injuries were on the rise throughout the sport, but also for a more eternal and less noble reason: nostalgia. Many fans who got to talking to one another in 1997 grew up watching the baseball of 1977 (1,678 starts on four days; 1,025 starts on three; just 670 on five) or of 1987 (2,297 on four days; 836 on five; 362 on three). They had seen the four-man rotation die out very quickly, and it didn’t seem right to them. They wanted to hold onto the version of the game they first learned.

Still, even in those conversations about whether to return to the four-man rotation, everyone acknowledged that four days’ rest was the standard for ‘regular’. Since Baseball Reference didn’t exist yet (and BP itself barely did, without the kind of data one would have consulted to find this), few probably knew the numbers, but the numbers backed them up on that.

Ten years later, they said something similar. There’d been a shift, but starts on four days were still 81% more common than starts on five. In 2017, that gap had shrunk to 41%, but that’s still a wide lead. Four days was regular rest even as recently as the last years before the pandemic.

But the data sing a different tune now. In 2026, there were 2,169 starts on five days’ rest, and just 1,411 on four days. Not only is five days 54% more common than four, but 1,039 starts came on six days of rest or more, making four days closer to being truly ‘short’ rest than to being regular. A small part of that can be chalked up to a schedule that became more forgiving of the extra day of rest starting in 2018, with four extra off days sprinkled into each team’s slate. Mostly, though, it reflects a shift in how teams think about recovery, performance and injury prevention. I wanted to see how uniform that shift is, and what differences exist between teams in how they think about the question.

Unsurprisingly, the most important variable in the question is the individual in question. The universal truth is that there’s no universal truth.