I remember Bill James getting all excited his first year, mostly because he was 20 years old. 20 year old position players who can play in the majors have a lot of upside. (And I'm not suspicious of the age: I assume the quality of documentation in Puerto Rico is pretty good, and he stuck around in the majors until he was 40.)

His top ten age 21 comps in bb-ref: Justin Upton, Andrew Jones, Miguel Cabrera, Juan Gonzalez, Dick Kokos (who?), Boog Powell, Jose Canseco, Willie Mays, Hank Aaron, Sam Crawford - a pretty distinguished list.

He had a breakout year at age 23: .162 games of 306/.347/.543 in the low-offense year of 1989, 146 OPS+, 5.7 WAR. Led the league in triples, RBI, total bases, and SLG, 2nd in the MVP vote to Yount.

His top 10 age 23 comps in bb-ref: Andruw Jones, Jose Canseco, Tony Conigliaro, Jack Clark, Juan Gonzalez, Cesar Cedeno, Boog Powell, Adrian Beltre, Del Ennis, Al Kaline. That's a list of players who (1) in general had very good careers, and (2) in most cases were considered disappointments in how their careers turned out after the start they had. Even Kaline fits into that.

But that 5.7 WAR for Sierra for that year was nearly half of his career total. He had one more good year at age 25 and then had negative WAR for the rest of his career. 1992-2006, 14 years in the majors, nearly 5000 PA - and a total WAR of -3.0. Amazing in its own way. (He missed one year out of the majors in all that, 1999 - it looks like he was in indy ball, playing for Atlantic City.)

I have a vague memory of Sierra's decline coinciding with his decision to bulk up and add power to his game. I remember him being pretty slim and athletic when he first came up. Then he got big one offseason and he seemed to slow down.

I had great hopes for him in Oakland when he showed up, but goodness he was terrible.

I have a vague memory of Sierra's decline coinciding with his decision to bulk up and add power to his game.

I also remember the complaints about Sierra's strength training ruining his game.

Here are a couple of quotations from Verducci's April 1994 season preview of the A's (SI Vault): "RF Ruben Sierra -- Too many muscles, not enough hits last year" and "Rightfielder Ruben Sierra batted a career-worst .233 after adding too much upper-body bulk."

It's funny to think almost all traditionalists now assume muscles (and the steroids that help build them) obviously must help hitters, but 17 years ago these people often believed the opposite. I wonder what the reaction would have been if Canseco had published "Juiced" in 1994. Would readers have thought Canseco was limiting his potential with all of his weight training?

I moved to Texas shortly after Sierra's career began, so I saw him a lot in his early years, and I was just as impressed as Bill James or anybody else. Sierra was not only an impressive athlete, but he really, really hustled ‐ he's still the guy I think of as busting it down the 1B line harder than anyone else, and he was very fast in the bargain. He had a good arm and great outfield range. Despite his later reputation as a sulky malcontent, he was in the lineup every day as a kid and played really hard.

I guess there were illusions at work, though, looking back. Sierra was always a better hitter RH than LH, so he was usually hitting at a platoon disadvantage. He hit .239 LH in 1988, and in his big 1989 season he hit .289 LH – not that .289 was bad, but it was a great season because he destroyed LHP batting right (.341/.378/.600). He really did have the Clemente hitting philosophy – he didn't walk very much, but he didn't strike out much either for his era. But when you hit .258 lifetime left-handed, you need to have outstanding power to be a really great player, and Sierra didn't have that, either. His career high in HR was 30, in the fluky year of 1987, when he was 21 years old.

Some guys don't extrapolate their early promise, and Sierra is one of them, the Garry Templeton crowd. They can get reputations for dogging it, but Sierra played hard in his later years too. He just wasn't as good a ballplayer as he initially seemed.

I was a big Sierra fan when he first came up. I still remember the big Sierra/Canseco trade. I miss blockbusters like that.

He's about the closest thing you'll find to a Joe Carter clone, his "most similar" player at BB-Ref.

Here are a few corner-OF and 1B comps.

A listing of the best single seasons by WAR from among the motley group in Dan's post:

Anderson 6.1
Carter 5.8
McInnis 5.8
Sierra 5.7
Anderson 5.3
McInnis 5.2
Tino 5.2
Sierra 5.0
Moses 4.8
Tino 4.6
McInnis 4.5
Surhoff 4.4
Carter 4.1
Moses 4.0

The problem is that after that - after the top two years - Sierra's dropoff is worse than everyone else on the list. (OK, I mostly didn't look at the really old-time guys.)

If we're taking applications for the HoVG, or at least the HoG, then:

Surhoff is a career candidate for that, not a peak candidate.
Anderson is a peak candidate - he had a nice two years there.
And a number of the other guys also look better on peak than on prime or career, including Sierra and Carter.

Oh, and how in the name of baseball did Bill Buckner get 10K plate appearances? Don't answer that ...