On-Base Percentage Leagues Primer (2021 Fantasy Baseball)
The industry standard fantasy baseball league has five offensive categories: runs scored, home runs, runs batted in, stolen bases, and batting average. Lots of rankings systems are based on this setup. However, lots of leagues tweak this a bit by changing batting average to on-base percentage. This change in isolation does not change things drastically, as batting average and OBP are highly correlated. However, there are exceptions. There are certain guys that see their projected impact change substantially in one direction or the other when shifting to OBP.
In this post, we’ll highlight a bunch of names, pointing out guys you should be moving up and down your board if you play in a league that uses on-base percentage. Let’s get into it.
For each player I highlight, I will show you their full-season paces (using 650 plate appearances) in each category based on what they’ve done the last two seasons.
The league average difference between batting average and on-base percentage is .069 points. Meaning a .280 hitter would, on average, have a .349 OBP. You can see Hoskins’ difference over the last seasons is an outrageous .126. That is because he has a 16% walk rate (the league average is around 8%). That’s the seventh-highest walk rate of the last two seasons for hitters with 300 or more plate appearances.
Switching your league from batting average to on-base percentage vaults Hoskins up the ranks from spot 85 to 56 when you do percentile ranks of each category and average them out. That’s a massive climb. As a guy with the raw power to club 40 homers and drive in 100 runs, Hoskins has massive upside when you eliminate the batting average category. If he falls outside of the top 70 hitters drafted, you should be all over him in OBP leagues.
Nimmo has the fourth-highest walk rate in the league over the last two seasons, drawing a walk in 16.5% of his plate appearances. You can see the huge disparity between his average and OBP. This makes him a very intriguing outfield target in OBP leagues.
The potential problem here is playing time. While right now Nimmo is projected to lead-off for the Mets against right-handed pitchers, that team has really bulked up this offseason, especially in the outfield. The additions of Jonathan Villar, Kevin Pillar, Albert Almora Jr., as well as the 2020 emergence of Dominic Smith could potentially send Nimmo to the bench quite a lot this year. That makes him hard to draft even at pick 256, but if he comes out leading off in Spring Training games and looking good, he is worth a bench spot flier on your OBP league fantasy team.
Muncy’s 2020 line looks pretty rough with a .192 batting average that came off the back of a .203 BABIP. However, you see the numbers above. His full-season pace makes him a great source of runs, homers, and RBI, and his OBP has stayed very useful even despite that crater 2020 average. His walk rate over the last two seasons has been 15.4%, another top-ten walk rate in the league.
The best part about Muncy is the draft cost has fallen quite a bit after 2020. You can get this guy after round eight in a lot of drafts, and he has all kinds of positional eligibility (has 1B, 2B, and 3B on some sites!). Muncy is probably the most appealing name on this list for OBP leagues, given all of the above.
Gallo was a huge disappointment in 2020, even in OBP leagues. His .301 OBP was just a killer, and it didn’t even come with a great home run total (he hit just 10, driving in 26 runs). Only two hitters have struck out at a higher rate than Gallo over the last two seasons (Miguel Sano and Chris Davis), but his 15.5% walk rate is still cause for optimism in the OBP category.
The most notable thing about Gallo is how cheap he is in 2021. In 2019 and 2020, Gallo had an ADP in the high 80’s. Now, after a short 2020 season, he’s fallen 80+ picks to 164. That makes him a super-steal in OBP leagues if you think he will get back near his prior self. He is a guy that could league the lead in homers while being fine in OBP and even stealing you a handful of bags.
Biggio just does not like to swing the bat. He consistently gets deep into counts, which results in tons of strikeouts (26%) and walks (16.1%). He had a really impressive 2020 season which has bloated his ADP up to 60. I’m not sure the numbers above justify that pick, and a lot has been made of his lack of exit velocity, which could make him a liability in home runs. The steals are a plus, though, so if you’re in an OBP league and you find yourself behind the eight-ball in steals, Biggio could make some sense to you there.
The most talked-about man in fantasy! Mondesi does one thing extremely well – steal bases, as you can tell by his 650 plate appearance pace of 64 steals above. The thing he does worst is drawing walks, with a 4.4% walk rate that is tied for 14th lowest in the league the last two seasons. That makes him an even worse target in OBP than in average. As we saw a bit in 2020, Mondesi can use some good luck and his speed to steal some base hits and post a non-terrible batting average, but you can pretty much bank on another sub 5% walk rate from him in 2021, which just makes him brutal in OBP.
If he steals 60 bags, he’ll be incredibly useful in fantasy this year, but with a top 30 ADP, I don’t think it’s a great idea.
Baez is right there with Mondesi in walk rate at 4.4%. The guy is as free-swinging as they come. His strikeout rate over the last two seasons is 29%, which explains that bad batting average. The good news for Baez is that he has shown the ability to hit for a decent batting average, hitting .290 in 2018. That’s likely to be a career-high with how often he strikes out, but at least you can see that he’s done it before.
His awful 2020 season (.203 batting average, .238 on-base percentage) has him cheaper than ever before but pick 72 is still pretty high for a guy that is likely to kill you in OBP while being just slightly above average in everything else.
Anderson’s batting average hasn’t made a ton of sense over the last two seasons with his 22% strikeout rate. He hits a ton of line drives and beats out a bunch of weak grounders, but it’s pretty ridiculous to expect anything over .300 from a guy that strikes out this much. Maybe he will continue to prove us wrong, and if he does, his OBP will be fine. However, if he comes down to a more reasonable .280 batting average, he’s going to kill you in OBP as he has the fourth-lowest walk rate in the league the last two seasons at 3.4%. The runs and steals will be there, but at pick 41, I think you can do better than a guy that could be negative in two categories.
Rosario switched teams over this offseason, which lowers his runs and RBI projection going from the elite Twins lineup to one of the league’s worst units in Cleveland. Rosario still feels too cheap at pick 113, given his ability to hit the long-ball and prominent spot in the Indians lineup. However, he’s not going to be a plus in OBP unless he majorly changes his approach. Over the last two seasons, he’s walked just 5.0% of the time, putting a lot of pressure on him to get base hits to keep his OBP up.
The young White Sox star is bursting with power upside and even showed the ability to hit for very high batting averages in the minors. The one thing he has never done is walk. His walk rate in his big league career so far is 5.7%. You can see that manifesting in a low .321 OBP so far. At the age of 24, there is lots of time for him to improve in plate discipline if he wants to, so I wouldn’t let this push Eloy too far down my draft board in 2020, but he does need to drop back a bit.
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