Roger Clemens is one of the greatest pitchers in Major League Baseball history, so he rightly gets most of the publicity among Stros pitchers. However, Roy Oswalt is currently the best pitcher on the Stros’ staff, one of the best pitchers in the National League and is well on his way to becoming the best Stros pitcher ever.
As noted in this recent post on Clemens, the statistic “runs saved against average” (“RSAA) is one of the best measures for evaluating a pitcher’s true effectiveness because it is based on the two most important things for a pitcher in winning baseball games — that is, not giving up runs and getting hitters out. RSAA measures the number of runs that a pitcher saves for his team relative to the number of runs that an average pitcher in the league would give up while obtaining an equivalent number of outs for his team. Inasmuch as the hypothetical average pitcher’s RSAA is always zero, a player can have an RSAA that is either a positive number — which indicates he is an above average pitcher (i.e., Clemens and Oswalt) — or an RSAA that is a negative number, which means he is performing below average (i.e., remember Brandon Duckworth and Tim Redding?).
Moreover, RSAA is a the best measure for comparing pitchers who played during different eras. Inasmuch as RSAA measures a pitcher’s ability against that of an average pitcher in the pitcher’s league for each particular season, a pitcher’s lifetime RSAA measures how that pitcher performed against the average pitcher of his era. That’s really the best way to compare pitchers from different eras because comparing other pitching statistics — such as earned run average, wins and hitting statistics against — is often skewed between pitchers of hitter-friendly eras (i.e., the era in which Clemens and Oswalt have pitched) versus pitchers of pitcher-friendly eras (i.e., such as the late 1960’s and early 70’s).
In pitching a complete game the other day against the Tigers, Oswalt attained another milestone by reaching 150 RSAA for his career. Roy O is easily the Stros career leader in RSAA:

1 Roy Oswalt 150
2 Billy Wagner 99
3 Roger Clemens 87
4 Mike Hampton 76
5 Dave Smith 75
6 Octavio Dotel 67
7 Nolan Ryan 60
8 Wade Miller 56
9 Don Wilson 55
10 Joe Sambito 53
But what is not as well known is that Oswalt is getting close to being in the National League’s top 10 list for career RSAA through the age of 28:
1 Christy Mathewson 279
2 Tom Seaver 234
3 Robin Roberts 229
4 Don Drysdale 219
5 Dizzy Dean 207
6 Ferguson Jenkins 196
7 Greg Maddux 189
8 Juan Marichal 177
9 Grover C Alexander 176
10 Jose Rijo 158
11 Roy Oswalt 150
Not bad company, eh? Barring injury, Oswalt is well on his way to a Hall of Fame career. He is signed through the 2007 season, but unless the Stros sign him to a long-term deal before the expiration of that deal, the best pitcher in Stros franchise history will become a free agent. Losing Roy O would be a serious blow to the Stros.
Oswalt’s career pitching statistics are set forth below and the abbreviations for each of those stats is set forth in pdf here.