John Brattain over at the Hardball Times wrote this well researched article about one of the most underappreciated Stros players of all-time, Jimmy Wynn.
Wynn — who was nicknamed “the Toy Cannon” — toiled for the Stros during the club’s difficult early years when the club was not blessed with much talent. Moreover, his career hitting numbers do not compare well with statistics of today’s sluggers because Wynn played in a different, more pitching dominated era (1963-77). Nevertheless, as Brattain points out, Wynn was one of the best centerfielders of his era:

I?ve often been amazed that Wynn never got more love from the BBWAA or the VC in Hall of Fame consideration. No, I?m not advocating him, but when I watched this little dynamo, I was always very impressed how he played the game.
When you consider that he played the bulk of his career in what were at the time the toughest hitter?s parks in the game (the Astrodome and Dodger Stadium) his 291 home runs looks very impressive. Wynn was a plus defender (albeit a rag arm which caused right fielder Joe Ferguson to cut in front of Wynn to make a catch with a runner on third during the 1974 World Series) with a terrific batting eye. He has a number of legitimate knocks against him: short career (6653 AB), no hardware save three All Star Game rings, just 26 post-season AB, no big career milestones etc.
According to Lee Sinins? sabermetric encyclopedia, Wynn was the second best (albeit a distant second) CF in the NL from 1960 to 1980 (using the “Runs Created Against Position” (“RCAA”) metric). If there was ever an “Unappreciated Player Hall-of-Fame,” I?m guessing Wynn would go in on the first ballot.

Brattain’s article points to another reason why the RCAA is particularly valuable to evaluate hitting ability across different eras. RCAA measures the two most important things in winning baseball games ? that is, creating runs and avoiding making outs — by computing the number of outs that a particular player uses in creating runs for his team. RCAA then compares that number to the amount of runs that an average player in the league would create while using an equivalent number of outs. Inasmuch as the hypothetical average player’s RCAA is always zero, a player can have either a positive RCAA — which indicates he is an above average hitter (i.e., Barry Bonds) — or a negative RCAA, which means he is performing below average (i.e., Brad Ausmus).
Thus, RCAA measures a player’s hitting ability against that of an average player each season and, as a result, a player’s lifetime RCAA reflects how well that player hit in comparison to an average player during that player’s career. Accordingly, Wynn’s RCAA reflects how well he compared to an average hitter during his era, just as the current Stros’ hitters’ RCAA reflects how they measure against the average player in today’s era. Inasmuch as Wynn was consistently in the top ten in the National League RCAA during a good part of his career — which is basically the stature of current players Bags, Bidg and Berkman during their prime seasons — the Toy Cannon remains one of the best Stros players of all-time.