If you focus on his age and overall production so far, the reported near-$100 million that the Red Sox are handing Pablo Sandoval for his next five years are reasonable. He’s a young man with an established bat at a scarce position. But if you focus instead on some of the aspects of his production, things look a little different. They look a little scarier.

First, read Dave Cameron on why even a sixth year wouldn’t have been crazy, given the right salary numbers. Basically, as the number of years go up, average annual value goes down. The sixth year might be the premium that gets the signature, but it’s not a sixth year at the same price as year one. Given that the salary pretty much exactly follows the breakdown that Cameron showed, this isn’t a terrible contract if you call Pablo Sandoval a 3.5-win 28-year-old third baseman. Even if it’s a little more than the median five-year $80 million contract the crowd wanted to give him.

But what if you call him other things?

Pablo Sandoval is a large baseball player.

It’s three years old, but Jeff Zimmerman once developed an aging curve for heavy players. He put players in bins based on Body Mass Index, or roughly weight divided by height. Then he looked at the average change, year-to-year, in his runs produced (measured by fielding, offense, and positional runs). The change in runs is on the y-axis, and the player’s age on the x-axis.

Sandoval is already in his decline phase — that’s usually true of free agents. But if you cite his age as a reason that he should be closer to his peak, then this graph is scary. Because the heavy player aging curve is shifted, and Pablo might age like a 30 year-old svelte player next year.

Pablo Sandoval is a large third baseman.

Really, this is just tied into the aging curve above, and maybe it’s not a real issue for the Red Sox, who don’t have a great long-term solution at first base anyway. But players as large as Sandoval don’t usually stay at third base. In fact, of the 68 players that have played at a listed weight over 240 pounds since 2002 (Sandoval is currently listed at 245 here), only two were third baseman for any amount of time: Scott Rolen and Joel Guzman. Guzman was seven inches taller and played 87 innings at third base. Rolen was five inches taller and is a stretch as a comp. Even Juan Uribe, not in the sample, is an inch taller, ten pounds lighter, and started as a shortstop.

It looks like Sandoval may be destined for another position before the life of this contract is up. In the end, that will sap value from his overall worth, even if the team can get value out of him at first base or designated hitter.

Pablo Sandoval is a large oft-injured third baseman.

Some might quibble with the label. The two biggest chunks of time that Sandoval has missed have been due to breaking the left and right hamate bones (possibly due to knob-grabbing), and he has no more hamate bones to break (“I got no more bones in there man,” as he put it to me last year). But that understates the case. Since 2012, he’s missed 59 days (including spring training) due to left foot and thigh strains among other things.

Another thing. Research that has looked at the fact that past injuries predict future injuries is agnostic of the specifics. And that research has found that there is such a thing as injury prone. Rob Arthur even created a regression equation that can help us predict how many days Sandoval will miss in 2015: 16.

That’s not that bad of course. But Sandoval’s body type has something to say about his chances of winding up on the disabled list. Thanks to Jeff Zimmerman’s DL database, we know that players over 240 pounds averaged 1.5 trips to the disabled list between 2002 and 2012. They averaged 66 days on the DL. Players under 240 pounds averaged .47 trips to the DL per year. They averaged 53 days on the DL. The sample size isn’t huge (that same 68 players), but the results are stark.

Pablo Sandoval is large oft-injured third baseman that makes his living on making contact on pitches outside the zone.

Over the last two years, Sandoval has been top-ten in making contact on pitches outside the zone. He’s legendary for swinging at anything from his teeth to his toes, but so far he’s made a living making contact on those pitches. At his age, you might think this could continue. Dunno about that. Check out the aging curve for hitter components, via Bill Petti and Jeff Zimmerman:

See that dark green line that plummets in the middle of the graph? That’s contact on pitches outside the zone. It begins to fall off precipitously at… 28 years old.

You could say that he’s falling from a nice peak in o-contact, but then there’s the fact that he has swung at nearly 46% of the pitches he’s seen outside the zone over his career (that number is about 50% worse than league average). He’s going to keep swinging at pitches that make you go ‘wut.’ But soon he’ll start missing them more.

Pablo Sandoval is large oft-injured third baseman that makes his living on making contact on pitches outside the zone and has a reputation for playing well in October.

I looked at Sandoval in the postseason, and if you ignore power results — and you should, because power becomes stable only in really large samples — there’s no difference between Regular Season Pablo and Postseason Pablo. Maybe he swings at a few more fastballs. But really you should probably bet on Pablo to be more like his 3533 regular season plate appearances than his 167 postseason ones.

——

Because the biggest, broadest definition of Pablo Sandoval is that of a three-to-four win third baseman, the deal probably makes sense. That isn’t to say that he isn’t without risk. And yes, most free agent deals come with risk, but this one seems to come with more than most. His size, his position, his skills at the plate, and his reputation — all of these things bring with them hefty asterisks.