As you surely know, the big baseball news of the week is that Major League Baseball and the MLB Players Association agreed upon a new Collective Bargaining Agreement, ensuring that more than two decades of labor peace will continue uninterrupted for at least five more seasons. Most of the largest changes came in tweaks to qualifying offers and the luxury tax, but there's one seemingly quiet change that could have some big repercussions on the field: The 15-day disabled list is reportedly turning into the 10-day disabled list.
How could five days -- and it's important to remember it is indeed days and not games -- matter that much? It's probably a bigger deal than you think, on both sides of the ball.
To start with, consider how this might affect how teams approach the starting rotation. In a five-man rotation, here's what a regular starting pitcher's schedule looks like following a start:
Days 1-4: Rest
Day 5: Start
Days 6-9: Rest
Day 10: Start
Simple, right? Two starts every 10 days. Now think about how that looks with even a single day off included. And, realize that we may get additional off-days under the new CBA, according to MLB.com's Richard Justice, who reported that "beginning in 2018, the regular season will begin in mid-week to create additional off-days during the schedule." So while we don't know how many more days off are coming, it seems that it's at least "more."
We'll randomly assign the team's off day to Day 7 in our hypothetical, but it could really just be about any day:
Days 1-4: Rest
Day 5: Start
Days 6-10: 4 days rest, 1 team off day
Day 11: Start
(In our scenario above we've simply pushed each starter back a day rather than skipping the fifth starter, but if that happened, then the same effect would take place for that fifth starter, who would continue to not get two starts in a 10-day period.)
See what just happened? The 10-day window now includes just a single start and nine days (eight games) of eating up a roster spot. Since the average Major League start was about 5 2/3 innings in 2016, that's a lot of wasted time for not a lot of return, and you can already see where this is going. It's extremely easy to envision scenarios that involve giving non-elite starters a 10-day break, foregoing that single start -- which, let's be honest, is probably less than 5 2/3 innings for most back-end starters -- in order to give that pitcher much-needed rest and add a fresh arm that the team can actually use for that stretch.
Strategically, it makes sense, and it might help further the trend that's been clear in baseball for some time, which is a further blurring of the line between "starters" and "relievers" to just have "pitchers." Let's be clear, here: This is not an invitation or expectation that teams will use the disabled list in anything other than good faith. It's a recognition of the fact that over a long season, just about every pitcher is dealing with aches and pains. If this leads to short breaks that keeps arms healthier and staffs better-utlitized, then all the better.

We could see a similar effect happen on the hitting side, where we've seen a plague in recent years of teams holding out some of their best players for a week or more in hopes of not having them be inactive for a full 15 days. Think about when Bryce Harper sat for a full week over the summer, resting a sore neck. Think about the Dodgers leaving an injured Mark Ellis on the bench until the 10th day, back in 2013. Think about how often the Mets played shorthanded in 2016 before finally putting Yoenis Céspedes on the disabled list with a sore quad.
That's a big deal in the age of 12- and 13-man (or, regrettably, sometimes 14-man) pitching staffs, where managers have gone into games with a short bench to begin with, then can't use the injured player and don't want to use the backup catcher, and find themselves completely handcuffed in the late innings. The Twins actually played a game in April with just two available reserve options -- catcher John Ryan Murphy and outfielder Eddie Rosario -- and they were hardly alone in doing so.
Consider this paragraph from a June 4 recap about a Mets game where they had outfielders Cespedes and Juan Lagares active, but unavailable:
"In Saturday's ninth, for example, [Terry] Collins turned to former college shortstop Jacob deGrom as a pinch-hitter with the bases loaded, simply because his bench was so depleted. Though deGrom popped up to end the inning, the Mets held on to win regardless."
This wasn't a blowout or an 18th-inning emergency. This was a three-run game in the ninth inning, and knowing that the Mets had no position players to hit for reliever Addison Reed, the Marlins simply walked Curtis Granderson to get to the pitcher's spot. deGrom is among the better-hitting pitchers, but he's still a pitcher.
Who wants that? No one wants that. Knowing that they'd have lost one of their players for just 10 days rather than 15 might have spurred the Mets to disable Lagares or Cespedes sooner than they actually did, adding a healthy hitter to Collins' roster. That's all upside, and very little downside, and it's of course not limited to just the Mets. It's good for the sport.
This is both a new change and a very old one, anyway. Baseball had a 10-day disabled list at various points through its history before it was permanently dropped in 1984. Now, it's back, and while it may not seem like much, there's a real chance this could have strong -- and mostly positive -- on-field effects.