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March 6, 2002

Doctoring The Numbers

Improvement Ratio

by Rany Jazayerli

In the last installment of DTN, we examined the topic of whether left-handed pitchers take longer to have a breakout season than right-handers do. In the process, we had to define exactly what a "breakout" season is. I used a series of qualifiers to define the term, and it worked pretty well. But there is a much simpler definition:

A breakout season is what Roy Halladay had in 2001.

Sure, a 5-3 record and a 3.16 ERA in 105 innings doesn't look that impressive on the surface...unless you consider that Halladay had a 10.64 ERA in 68 innings in 2000, the worst ERA in major-league history for someone with even 40 innings. Here is a list of the worst single-season ERAs since 1900:


Year Pitcher          IP    ERA
2000 Roy Halladay   67.2  10.64
1999 Micah Bowie      51  10.24
1973 Steve Blass    88.2   9.85
1998 Andy Larkin    74.2   9.64
1985 Glen Cook        40   9.45

Halladay improved his ERA by 7.48 points in 2001, which--not surprisingly--is a record for anyone with 50 or more innings in two consecutive seasons. What is surprising is the margin by which this is a record:


Pitcher         Year 1    ERA  Year 2    ERA   Diff
Roy Halladay      2000  10.64    2001   3.16   7.48
Willis Hudlin     1936   9.00    1937   4.10   4.90
John D'Acquisto   1977   6.54    1978   2.13   4.41
Albie Lopez       1997   6.93    1998   2.60   4.33
Ferdie Schupp     1915   5.10    1916   0.90   4.20

(On a pure percentage basis, it's hard to imagine anyone cutting their ERA by more than Ferdie Schupp, who sliced 82% off his ERA in 1916. He threw just 140 innings in 1916, preventing him from holding the single-season record for ERA.)

It's not just Halladay's massive improvement in his ERA that is so eye-catching, though. After all, looking at Halladay's career numbers, his 2000 season stands out for its overall suckitude. In 1999, Halladay had 3.92 ERA; he gave up just three earned runs in 14 innings in his 1998 cup of coffee, and came within an out of a no-hitter on the season's final day.

No, what makes Halladay's 2001 performance stand out in bold relief from the rest of his career is not his ERA. It's his strikeout-to-walk ratio.

Here are Halladay's walk and strikeout numbers, year by year:


Year    BB   K
1998     2  13
1999    79  82
2000    42  44
Total  123 139

Moreover, this fits perfectly with the trend Halladay showed in the minors, where he was considered a top prospect despite his maddeningly unimpressive strikeout-to-walk ratios in Triple-A. In 1998, he had 71 strikeouts against 53 walks; in 1997, he had 64 strikeouts against 53 walks. (In fairness, his ratios in the low minors were much better.)

Going into 2000, Halladay's career K/BB ratio in the majors was just 1.13. To put that in perspective, the lowest K/BB ratios of any active pitcher (min: 200 IP) through 2000 were:


Pitcher           BB   K  Ratio
Jamey Wright     349 335  0.960
Steve Sparks     307 333  1.085
Jason Grimsley   345 385  1.116
Roy Halladay     123 139  1.130
Dennis Springer  288 254  1.134

Greg Maddux and Bret Saberhagen, these guys are not. These five pitchers include a pair of knuckleballers and a Rocky Mountain refugee, and what a man with Halladay's stuff was doing on this list isn't entirely clear. To his credit, last season he orchestrated one of the most impressive leaps in K/BB ratio in history.

Halladay's ratios, through 2000 and in 2001:


Years        BB    K  Ratio
1997-2000   123  139   1.13
2001         25   96   3.84

That's a remarkable difference. Halladay more than tripled his career strikeout-to-walk ratio in 2001. That's more than remarkable: it's historic. The following chart lists the greatest improvements in K/BB ratio over a pitcher's previous career norms. To qualify, a pitcher had to throw at least 100 innings in his year of improvement, and have at least 200 previous career innings:


                          --- Season ---  ---- Career ----
Pitcher         Year Age  BB    K   K/BB   BB     K   K/BB  Ratio
Hal Brown       1963  38   8   68  8.500  355   589  1.659  5.123
Jack Chesbro    1901  27  52  129  2.481  138    84  0.609  4.076
Cy Young        1904  37  29  200  6.897  931  1734  1.863  3.703
Bill Henry      1959  31  26  115  4.423  156   198  1.269  3.485
Rudy May        1982  37  14   85  6.071  932  1659  1.780  3.411
Red Donahue     1903  30  34   96  2.824  528   438  0.830  3.404
Roy Halladay    2001  24  25   96  3.840  123   139  1.130  3.398

Halladay ranks eighth behind a group of veteran pitchers who suddenly stopped walking people entirely (Cy Young actually qualifies for the list again in 1905, but he was excluded for the sake of brevity.)

There's another way to construct this study. K/BB ratio is a wonderful metric, but it is subject to distortion at the extremes. In particular, a pitcher who is able to cut his walks down to a bare minimum can dramatically increase his K/BB ratio even if his strikeouts don't budge. Consider a pitcher with 20 walks and 70 strikeouts, a ratio of 3.50. If he adds 10 strikeouts to his total, his ratio inches up to 4.00. On the other hand, if he cuts 10 walks, his ratio doubles to 7.00. Hal Brown didn't suddenly turn the corner at age 38. In his "breakout season," he struck out 68 batters in 141 innings, less than one every other inning. But because his control was freakishly impeccable for one fluky season (just 0.57 walks per nine innings), he reached the top of the previous chart.

That's not what Halladay did. Halladay's performance--cutting his walk rate and increasing his strikeout rate--was far more impressive. So instead of comparing strikeouts to walks, let's compare each of them to innings pitched.


Years       IP   BB    K  BB/G   K/G
1997-00    231  123  139  4.79  5.42
2001     105.1   25   96  2.14  8.20
Diff                      2.65  2.78

Halladay cut his previous career walk rate by more than two-and-a-half walks per nine innings, and increased his strikeout rate by an even higher margin. If we take the weighted average of the two (using an identical process to the one that turns homers and stolen bases into Bill James' Power-Speed number), we arrive at an "Improvement Ratio" of 2.72. This is the highest recorded by any pitcher, at any age, in major-league history.


Pitcher          Year  BB Imp   K Imp  Imp Ratio
Roy Halladay     2001   2.656   2.787      2.720
Randy Johnson    1995   2.257   2.733      2.473
Todd Van Poppel  1995   3.063   1.976      2.402
Jim Maloney      1963   2.164   2.621      2.371
Charlie Puleo    1987   2.274   2.392      2.295
Duane Ward       1991   1.549   2.999      2.043
Randy Johnson    1993   2.221   1.856      2.022
Jack Kramer      1944   2.622   1.627      2.008
Pedro Martinez   1999   1.368   3.616      1.985
Hal Newhouser    1946   1.458   2.679      1.888

Todd Van Poppel standing side-by-side with Randy Johnson, Charlie Puleo giving back cuts to Duane Ward...that's, um, a rather eclectic group of pitchers.

In general, the fluke seasons are vastly outnumbered by the truly great pitchers coming into their own. If we eliminate Van Poppel, Puleo, and Jack Kramer (a journeyman pitcher benefiting from the decreased talent level during World War II), we're left with a Hall of Famer (Hal Newhouser), two future ones (Johnson and Pedro Martinez), one of the better starters of the 1960s (Jim Maloney), and Duane Ward, who in the early 1990s might have been the best set-up man in baseball history.

If we extend the list, that trend becomes even more pronounced. Forty-one men have posted an Improvement Ratio of 1.5 or higher. Those 41 pitchers include Kevin Brown, Jack Chesbro, Rich Gossage, Sandy Koufax, Greg Maddux, Sudden Sam McDowell, J.R. Richard, Nolan Ryan, John Smoltz, Mario Soto, Dazzy Vance--and five different iterations of Randy Johnson.

Whatever Halladay started doing differently last year, let's hope he keeps doing it, because he's on to something big. The path he's following has been covered by some of the great pitchers in baseball history. But let's not get too excited yet. Remember, Todd Van Poppel once walked this way, too.

Rany Jazayerli, M.D. is an author of Baseball Prospectus. You can contact him by clicking here.

Rany Jazayerli is an author of Baseball Prospectus. 
Click here to see Rany's other articles. You can contact Rany by clicking here

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