2021 MLB Reflection and League Trends

October 11, 2021

Jon Anderson looks at the big picture of the 2021 MLB season by identifying leaguewide trends and high-level statistics.

Here at RotoBaller, we give you fantasy baseball coverage twelve months a year. The playoffs are still in full swing, which means it's probably not quite time to shift our focus to the 2022 season, but it won't be long before we're there.

In the meantime, we want to spend some time reflecting on the 2021 season. Before we go into the granular data, the team and player-specific data, it's important to establish the league context. I wanted to put this piece together taking a high-level look at the 2021 season. Did we see any significant changes to the league averages? Did the alleged new baseball bring down homers? Did the foreign substance crackdown make an in-season difference? We'll find out.

We will start as big as possible and start to narrow downward, but we won't get into the individual weeds here. Let's get to it.

Five Year Trends

This graph is a little bit counter-intuitive. A higher PA/HR number would actually mean fewer home runs since that shows it took more plate appearances to generate a home run. You can see that, indeed, home runs have been less frequent in the last two seasons after league records were shattered in 2019. It's not surprising that 2020 and 2021 would check in with slower homer rates than 2019, and it's important to note that the league was significantly ahead of the 2018 pace, but things are back to about a 30 PA/HR pace rather than the 27 established in 2019.

No huge differences in walks or strikeouts. We were seeing rapidly rising strikeout rates, but that trend was broken in 2021 as the league strikeout rate dropped slightly to 23.2%. Walks also came down after a weird year in 2020 when they spiked above 9% after really setting down at 8.5%-8.6% in the three years prior.

We also saw fewer stolen bases in 2021 after a spike in 2020. This year tied 2019 for the slowest steal rate in the last five years, with a steal happening every 82 plate appearances on average.

2021 by Month

One of the biggest stories of the 2021 season was the crackdown on foreign substances being used by starting pitchers. In late June, pitchers were subject to random checks for illegal substances on their person. This led to lots of speculation about spin rates taking a sudden downturn, bringing down strikeouts with it.

Indeed, strikeouts did decline after May pretty significantly. We went from 24.5% in April the whole way down to 22.7% in July and August. The league is more than happy to change the rules from year to year, so maybe we'll see them stop the random checks for substances, but more than likely this rule will stay and we'll be planning on more of a 22-23% league average strikeout rate in 2022.

Starting Pitcher Innings

Predictably, we saw another low year for starting pitcher innings workloads. Starting pitchers threw just 57.2% of the league's total innings, ceding 42.8% to relievers. That was up from 2020's total of 53.9% of innings thrown by the starter,  but a little bit below 2019's number of 57.9%.

These numbers can be a little bit misleading. Teams did not limit their starters by pulling them from games earlier as much as they did by just putting them out there less frequently. We saw quite a few teams go to the six-man rotation for periods of the year. 396 different players started a game this year, an average of 13.2 per team.

For fantasy purposes, we were and are most concerned about how many innings you're getting out of the fantasy-relevant starters. Only four names cracked the elusive 200 innings pitched mark, with only three more coming in above 190. Here's a list of every pitcher that pitched 170 or more innings this year:

That's a pretty staggering chart, although not really that surprising given our expectations coming into this year. The lack of innings from the league's starters certainly made the guys at the top of the list all the more valuable, especially in the case of Zack Wheeler and Walker Buehler who were dominant on the hill.

What does this mean for next year? I'm not sure. I don't think we should get overly concerned about it since it's league-wide rather than situational, and you never really know who the guys are going to be that can go for 200+. It would bump up slightly the guys that are on the list this year since they've established their arms as strong enough to go through that, but I do imagine that we see higher totals next year as we get another year removed from the weird 2020 season.

Team Disparities

Another thing that has been changing over the last decade or so is the wild disparities in team performance. Growing revenues, as well as wild differences in market sizes and other economic factors, have really driven some teams to polar opposites of the spending spectrum. This is nothing new, but I think we may have seen 2020 exasperate this divide. Teams were unable to generate revenue through game attendance, and the population did a lot less spending on entertainment overall as millions of people struggled with their own economic situations. Without getting too political about things, I think this actually worked to the previously rich teams' favor.

Just taking runs scored, you can see how great the difference was between the top of the league and the bottom.

Of course, the Tampa Bay Rays continue to cause major problems for the "it's all about money" crowd, and the Blue Jays and Giants also had great years without massive payrolls. However, you see just how pathetically bad the Rangers, Marlins, and Pirates were. Those things don't figure to change much moving forward. The MLB could institute some kind of salary floor to help this a little bit, but that's unlikely to happen and it would be unlikely to make a huge difference anyway.

This factors into the fantasy game by making it all the more important to draft players from teams you can expect to be successful. No matter how good Bryan Reynolds, for example, was this year, there was just a serious limitation on what he could do for your fantasy team, considering you are looking for runs and RBI from your players and that depends a lot on team context. I imagine we see much of the same for years to come, and fantasy managers will be best served taking note of it.

I hope this post has helped set the stage a bit for the rest of our 2021 reflection. Keep checking back as we have a lot of great baseball content coming at you all offseason!

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