BP Unfiltered: Strasburg’s Minor League Performance

Last year's #1 pick, Stephen Strasburg. makes his hotly-anticipated debut tonight, after a dazzling run through the minor leagues. Just how dazzling is the topic for today.

Here's his stat line, the way I look at it on my home computer, in real terms

Stephen Strasburg             Born 19880720 Age 21    Bats R    Throws R  Height  76 Weight 220  No DT, Real
Year Team         Lge  G  GS  IP   H  ER  HR  BB  K  GB%  DERA  W  L SV  H/9 HR/9 BB/9  K/9  NERA  PERA  LFRA DLH DLR STF  RAR
2010 Harrisburg__ Eas  5  5  22.0  13  4   0   6  27  68  1.64  3  1  0  5.3  0.0  2.5 11.0  3.68  1.78  3.15  -3   5  48   9
2010 Syracuse____ Int  6  6  33.3  18  4   1   7  38  64  1.08  4  1  0  4.9  0.3  1.9 10.3  1.35  1.51  3.49  -7  -1  64  14
              --------------------------------------------------------------------------------------------------------
             Minors   11 11  55.3  31  8   1  13  65  63  1.30  7  2  0  5.0  0.2  2.1 10.6  2.28  1.61  3.39 -10   4  58  23

and in translation

Stephen Strasburg             Born 19880720 Age 21    Bats R    Throws R  Height  76 Weight 220  Regular PDT
Year Team         Lge  G  GS  IP   H   ER  HR  BB  K  GB%  DERA  W  L SV  H/9 HR/9 BB/9  K/9  NERA  PERA  LFRA DLH DLR STF  RAR
2010 Harrisburg__ Eas  5  5  21.3  15  10   1   6  19  64  4.22  1  1  0  6.3  0.4  2.5  8.0  4.64  2.47  3.46  -3   5  37   5
2010 Syracuse____ Int  6  6  32.7  19   7   2   7  28  64  1.93  3  1  0  5.2  0.6  1.9  7.7  1.93  2.18  3.68  -7  -1  55  12
              --------------------------------------------------------------------------------------------------------
             Minors   11 11  54.0  34  17   3  13  47  63  2.83  4  2  0  5.7  0.5  2.2  7.8  3.00  2.29  3.61 -10   4  48  18

The first thing most stat-minded people look at on a pitcher are the K/BB rates. Strasburg's numbers are very good here, but far from unprecedented; plenty of people each year get 10 K/9 innings, especially in the low minors, plenty more put up BB/9 numbers in the ones. There's no reason for unusual excitement in those numbers.

What is exciting and different are his hits allowed numbers. A rate around 5 is pretty much at the top of the historical charts, driven by a phenomenal BABIP – or, as I prefer to look at it, a negative 10 DLH. DLH stands for "delta hits"; it is simply the number of hits he is above or below the average BABIP for his team. I prefer having the mix of rate stat and playing time that delta-hits gives. Now, it is fashionable to refer to any non-zero DLHs as "luck" – good luck in the case of a negative DLH, bad luck in the case of a positive DLH – and it is true that DLH scores tend to regress towards zero.

I'm not convinced that this is the case for Strasburg. A low DLH can also be the result of weak contact; that's the reason why knuckleballers regularly run up low BABIPs. There's evidence that minor league hitters were simply unable to make solid contact with Strasburg's pitches. The extra base hit rate is exceptional – among his 31 hits allowed, only 5 went for extra bases (three doubles, one triple, one homer). An average pitcher with 31 hits in the Eastern and International Leagues would give up nearly 7 doubles and 3 home runs, ending up with a little more than 10 extra base hits. Of 44 balls hit in the air, only 12 were classified as line drives (23 flies, 9 popups); a normal distribution of 44 balls in the air would have 16 line drives and only six pops. Given that he's been an extreme ground ball pitcher, the ratios per batted ball would be even more extreme.

A direct result of the low number of hits allowed is a very low number of runs allowed and, to take it a step farther, a low number of expected runs allowed. The PERA category is Peripheral ERA; basically, it is True Runs, applied to the pitching stats. If we're using a league where we have play-by-play data, it uses the real atbats, doubles, triples, and stolen base data; if not, it will use the league hitting data to make a rough guess for those values. We're using it here to see how many runs we should have expected this pitcher to give up, given the number of hits and home runs he actually allowed (unlike SIERA, which would use expected hits and home runs). Strasburg's PERA is outstanding; the list of pitchers who could hold a 1.61 PERA for 50 innings, while working primarily as a starter, only gets 16 names; 16 players between 1980 and 2010, about one every other year.

(real, untranslated performances)

Name             Age Year  Tm Lge  G GS   IP   H  ER HR BB  K  GB%  DERA  W  L SV  H/9 HR/9 BB/9  K/9  NERA  PERA  LFRA DLH DLR 
Dennis_Burlingame 20 1989 DUR CRL 11 11  54.3  28  3  1  5  42  -1  0.50  4  0  0  4.6  0.2  0.8  7.0  1.33  1.21  4.01 -13   1 
Dody_Rather       20 1985 ONE NYP  8  8  58.0  22  2  1 16  88  -1  0.31  8  0  0  3.4  0.2  2.5 13.7  0.78  1.24  2.77  -5  -3 
Paul_Rigdon       23 1999 AKR EAS  8  7  50.0  20  5  2 10  25  -1  0.90  7  0  0  3.6  0.4  1.8  4.5  0.90  1.25  5.55 -22  -2 
Charlie_Lea       23 1980 MEM SOU  9  9  75.0  34  7  0 21  54  -1  0.84  9  0  0  4.1  0.0  2.5  6.5  1.20  1.30  4.66 -23  -1 
Steve_Schrenk     24 1993 BIR SOU  8  8  61.7  31  8  2  7  51  -1  1.17  5  1  0  4.5  0.3  1.0  7.4  1.61  1.33  3.93 -16   2 
Josh_Beckett      21 2001 BRV FSL 13 12  65.7  32  9  0 15 101  -1  1.23  6  0  0  4.4  0.0  2.1 13.8  1.78  1.34  3.00  -4   3 
Mark_Tranberg     25 1994 CLR FSL  9  8  63.3  33  1  0 11  41  -1  0.14  7  1  0  4.7  0.0  1.6  5.8  0.85  1.35  4.93 -16  -3 
Frank_Castillo    19 1988 PEO MDW  9  8  51.0  25  4  1 10  58  -1  0.71  6  1  0  4.4  0.2  1.8 10.2  0.88  1.43  3.25  -7  -3 
Rick_Ankiel       21 2001 JCY APL 14 14  87.7  42 13  1 18 158  -1  1.33  5  3  0  4.3  0.1  1.8 16.2  2.05  1.44  2.40  -5   6 
Cole_Hamels       19 2003 LWD SAL 13 13  74.7  32  7  0 25 115  -1  0.84  6  1  0  3.9  0.0  3.0 13.9  0.96  1.47  3.25  -4  -4 
Kyle_Nicholson    22 2008 GIA AZL 11 11  62.7  34  8  1  3  54  79  1.15  6  1  0  4.9  0.1  0.4  7.8  1.44  1.47  3.81 -17   0 
Ted_Lilly         20 1996 YAK NWN 13  8  53.7  25  5  0 14  75  -1  0.84  4  0  0  4.2  0.0  2.3 12.6  1.51  1.47  3.33  -7   0 
Brian_Meadows     27 2003 NAS PCL  9  8  51.0  32  8  2  0  40  -1  1.41  7  0  0  5.6  0.4  0.0  7.1  1.94  1.50  3.46 -11   3 
Kevin_Slowey      22 2006 FTM FSL 14 14  89.0  52 10  2  9  99  41  1.01  4  2  0  5.3  0.2  0.9 10.0  1.92  1.51  3.72 -15   4 
Brian_Barnes      22 1989 WPB FSL  7  7  50.0  25  4  0 16  67  -1  0.72  4  3  0  4.5  0.0  2.9 12.1  1.62  1.55  3.52  -4   0 
Stephen_Strasburg 21 2010 multi   11 11  55.3  31  8  1 13  65  63  1.30  7  2  0  5.0  0.2  2.1 10.6  2.28  1.61  3.39 -10   4 

That's everyone with a real PERA under 1.70 for at least 50 innings, either at one location or over multiple teams (Strasburg has worked at AA and AAA; Brian Barnes also pitched two games in AAA and one in short-season A as well, with a total PERA of 1.66, the only other player who managed the feat combining across multiple teams). While there are some good pitchers on the list – Josh Beckett, Cole Hamels, Ted Lilly – it is largely a collection of forgotten pitchers. Most accomplished the feat at a low level – Strasburg and Meadows are the only ones on the list who played at AAA. They are frequently older; the three who played at AA, besides Strasburg, were at least 23. Looking at the data in translation will help clear out some of the clutter. Again, the list is dominated by relievers, but

Name             Age Year Tm  Lge   G  GS   IP   H   ER  HR  BB  K  GB%  DERA  W  L SV  H/9 HR/9 BB/9  K/9  NERA  PERA  LFRA DLH DLR 
Cliff_Lee         31 2010 multi     8   8  58.7  51  21   1   3  45  40  3.54  5  2  0  8.1  0.2  0.5  7.1  3.22  2.00  3.32  -1   6
Pedro_Martinez    28 2000 BOS AL   29  29 207.7 134  42  14  26 229  48  1.82 20  3  0  5.8  0.6  1.1  9.9  1.78  2.08  2.82 -22  -2
Ubaldo_Jimenez    26 2010 COL NL   11  11  76.0  47   9   1  22  60  57  1.07  8  0  0  5.6  0.1  2.6  7.1  1.07  2.08  4.21 -13 -10
Greg_Maddux       28 1994 ATL NL   25  25 191.7 146  47   5  29 137  62  2.21 17  4  0  6.9  0.2  1.4  6.4  2.25  2.11  3.62 -19  -2
Greg_Maddux       29 1995 ATL NL   28  28 198.7 145  44   9  22 154  66  1.99 18  4  0  6.6  0.4  1.0  7.0  1.95  2.13  3.38 -24  -6
Pedro_Martinez    27 1999 BOS AL   31  29 203.3 170  50   8  30 245  48  2.21 19  4  0  7.5  0.4  1.3 10.8  2.17  2.17  2.23  17   2
Pedro_Martinez    29 2001 BOS AL   18  18 112.0  86  29   5  23 127  52  2.33  9  3  0  6.9  0.4  1.8 10.2  2.57  2.25  2.41   2   4
Roger_Clemens     27 1990 BOS AL   31  31 225.0 175  63   7  46 218  53  2.52 19  6  0  7.0  0.3  1.8  8.7  2.52  2.25  3.68  -5  -9
Stephen_Strasburg 21 2010 multi    11  11  54.0  34  17   3  13  47  64  2.83  4  2  0  5.7  0.5  2.2  7.8  3.00  2.29  3.59 -10   4

THAT is impressive company. Strasburg is the first minor league pitcher to sustain a translated 2.30 PERA over 50 innings but, interestingly enough, is only the third-best pitcher in 2010. Everyone is noticing Ubaldo Jimenez these days, but Cliff Lee's performance (which includes one rehab start in AAA Tacoma) has slid under people's radar. To get to the next minor league pitcher on the list, you have to go down to

Name             Age Year Tm  Lge   G  GS   IP   H   ER  HR  BB  K  GB%  DERA  W  L SV  H/9 HR/9 BB/9  K/9  NERA  PERA  LFRA DLH DLR 
Roger_Clemens     20 1983 FSL/EAS  11  11  75.3  59  17   4  12  76  -1  2.03  7  1  0  7.0  0.5  1.4  9.1  2.03  2.37  3.22  -3  -4

OK. We should be pretty excited.