MLB: Before You Draft Mondesi...

In many ways the debate about Adalberto Mondesi is both exhausting and exhausted. We are at the point of the offseason where everyone knows the arguments on both sides; his upside is a top-five player, if not the most valuable player in fantasy. A 20-80 season at a time when speed is scarce is worth its weight in gold. Moreover, get Mondesi and you can largely ignore speed the rest of your draft — avoiding overpaying for rabbits who just can't hit. His speed also gives Mondesi a massive floor: even if the power dips down, a healthy Mondesi is almost guaranteed to steal 50 if not 60 bases (he's averaged 59 per 162 games in his career to date), making him worth an early pick, even in the worst-case scenario.

On the other side of the argument is a combination of Mondesi's health track record — he's never made it to 450 plate appearances. His batting average — he's a career .251 hitter, not ideal for an early pick, and it's unlikely to improve as long as he strikes out 30% of the time.

Those are the arguments, everyone knows them, no need to rehash them. 

Except I think there are two big arguments about Mondesi missing from the discussion so far that need to be looked at before you draft him this year.

Historical Context

Since 1960, there have been 218 seasons where a player stole 50 or more bases. If you're drafting Mondesi, you are counting on him joining this list.

Of those 218 players, only one of them had an OBP under .280. Two players had an OBP under .290 and seven players — out of 218 — had an OBP under .300.

Mondesi's career OBP is .284. "But he's getting better," you say. His OBP in 2020 was .294. Public projection systems all have his projected OBP under .300. In other words, what you're paying for in Mondesi — a player who steals 50 bases but gets on base less than 30% of the time — is nearly unprecedented in modern baseball.

Now, just because something has never (or barely ever) been done before doesn't mean it can't or won't happen. I do think it's a good idea if you're counting on a historic (or near historic) event to unfold, to pause and ask yourself if you really think this player is about to do something that almost every other player in history couldn't do.

"Walks shmalks, Rob. Mondesi gets barrels too — unlike these other guys on the list he has speed and pop, that's what makes him so valuable in fantasy."

Mondesi's career wOBA is .296. His public projections for 2021 range from a .292 to a .307 wOBA. Of the 218 hitters who have stolen 50 in this era, only 18 did so with a sub-.292 wOBA, 27 with a sub-.296 wOBA. 

In other words, Mondesi may not be the worst hitter to ever steal 50 bases (there are some bad hitters on this list), but he's close. 

It goes without saying, Mondesi is almost guaranteed to have the highest strikeout rate of any player who has stolen 50 bases if he makes this list. The worst of the 218 is Jonathan Villar's 25.6 K% in 2018. 

When you put the near historically low OBP together with the 5th percentile wOBA and the highest strikeout rate any elite base stealer has ever had, at least appreciate how hard and improbable what he's trying to pull off is before dismissing it as irrelevant to fantasy.

The Low OBP Really Matters

To state the obvious, there are three components that go into how many bases a player steals in a year:

1. How many stolen base opportunities they have
2. How often they take advantage of those opportunities
3. How often they are successful stealing the base once they decide to run

Let's break down these three components for Mondesi in 2021. In his career, Mondesi has been successful on 82% of his stolen base attempts — I'm going to assume that as a given for 2021, acknowledging it could be a little bit higher or lower in any given year, but 82% is a pretty good assumption for a talented base runner like Mondesi.

How many opportunities will he have? Let's start with how many he's had over his career to date:

Stolen Base Opportunities is a Baseball-Reference stat defined as "Plate appearances through which a runner was on first or second with the next base open." It's not a perfect stat by any imagination, but it gets at what we're looking for.

Over his career, Mondesi has had just over one stolen base opportunity per game. How does that compare to other top base stealers? Trea Turner has had 1021 stolen base opportunities in his career in 541 games played. That means Turner has had almost two stolen base opportunities per game compared to one per game for Mondesi. 

So why has Mondesi been such a prolific base stealer in his career despite so few stolen base opportunities? Not surprisingly, he's run at an extraordinary rate.

For his career, Mondesi has attempted a steal almost 43% of the time he's had an opportunity. Last year, it got all the way up to 54%. That's a massive rate.

Let's put this math together: let's assume Mondesi stays healthy all year in 2021 and plays in 150 games. Amazing. Let's assume he continues to get 1.1 opportunities per game (and I fully acknowledge that Mondesi is young enough to improve his approach and get on base more often than he has to date) — that's 165 stolen base opportunities. If he runs at his career 43% rate and is successful 82% of the time (again, his career success rate) that means Adalberto Mondesi just stole you 58 bases — congratulations, your bet on Mondesi paid off.

Here's the thing, when you study stolen base rates, barely any player maintains a rate as high as Mondesi's. Trea Turner runs 20% of the time. He's a pretty good and aggressive base stealer. If Mondesi plays in 150 games and steals a base as often as Trea Turner (20% of the time), suddenly he's only stolen 27 bases in a 150 game season. Jose Ramirez steals 13% of the time — Mondesi doesn't break 20 steals at that rate (you see why on-base-percentage sort of matters?). Let me repeat this for emphasis, if Mondesi plays a full season with his current on-base skills staying constant and runs as often as Trea Turner does, he wouldn't steal 30 bases. If he runs as often as Jose Ramirez he wouldn't steal 20. This isn't me making a prediction, it's just math.

You think I'm cherry-picking my examples. Rickey Henderson — the best base stealer of all time — stole a base 31% of the time in his career. If Mondesi starts stealing bases ONLY as frequently as Rickey Henderson, he's at 42 steals (again, this is in a full season for Mondesi stealing at the rate of the greatest base stealer of all time). When Rickey was 25 (Mondesi's age this year) he ran 34% of the time, which would bump him to 46.   

I'm not saying it's impossible that Mondesi keeps up his current clip, Vince Coleman ran 47% of the time. It was of course a vastly different era in the '80s, but it's possible. It is far more likely that Mondesi runs less often than he has during his career to date. If he does, because he gets so few opportunities, the floor on his steals is actually much lower than you may think.

Nothing here should be taken as a reason not to draft Mondesi. These are reasons to at least think it over one more time before you do.