We know that if there is a season in 2020 that it will be heavily shortened. Of course, a baseball season that doesn't start until July will obviously be much shorter. But a shorter season brings up the question of whether teams will adopt a 4 man rotation.
Most of this depends on the number of games played. I think that it will be 65 games, but that's just a guess. I'll be using 65 games as the number of games that will be played.
Teams have stopped using pitchers past the 6th inning. It only makes sense. If a team has a better pitcher to put in, why not put in the better pitcher? Teams have guys that can be really good for 1 or 2 innings, and then hand the ball to the closer to finish the game. It makes strategical sense.
Of course, with a drop of innings comes a drop of games. And these 2 aren't directly related, but pitchers using higher velocity pitches is the short explanation as to why pitchers get injured more often, and only start 30 games a year.
In the World Series, teams usually adopt a 3 or 4 man rotation. Whether it's the Scherzer-Strasburg-Gonzalez rotation or the Kershaw-Buehler-Ryu rotation, teams generally have to have guys that can go for more than 5 innings. Especially in the Postseason where teams get into their bullpen earlier, it's important to have quality starters. And that's a general rule of thumb, good teams have quality starters.
But what makes a quality starter? It's a guy that can go 6 innings without sacrificing on velocity or control. When a starter goes 6 innings and is obviously tired, a manager faces a tough decision. Keep the starter in and risk runs, or sacrifice the bullpen's better relievers. If the team is in a situation that matters enough to make the sacrifice, the answer is to pull the starter. But because teams generally aren't in those situations where the game matters above anything else, the answer is usually to keep the starter in the game.
That's where a quality starter comes in. A team needs a guy that will remain consistently decent throughout 7 innings. Obviously, games aren't always close, and sometimes starters can get pulled early.
Especially if a team uses the opener, it's important to have quality starters. The bullpen will not always be available either, because in general teams have a 5 man rotation filled with pitchers that go 5 or 6 innings. Teams need quality starters.
What is the best way to make a pitcher a quality starter? They need to get rest. There's no way that a pitcher will be able to go for even 6 innings on a daily basis. Only getting 2 or 3 days of rest isn't enough. Teams will have to go into their bullpens earlier, so adopting a 4 man rotation isn't the right choice.
There's also up and coming prospects like Brusdar Graterol who might not be able to get into a rotation with the Dodgers, who have Clayton Kershaw, Walker Buehler, and Ross Stripling. And Graterol is just one example.
So I don't think that teams should adopt a 4 man rotation. I would take a 5th starter over a starter that can only go 4 innings.