What Batter Had The Best September Since 1914?

I used the Baseball Reference Play Index to call up all the cases of 90+ PAs that had an OPS+ (in this case called sOPS+) of at least 250 for September (actually, Sept/Oct). As far as I can tell, that is OPS adjusted for the league average and park effects (UPDATE 8-3-2015: BR informs me that sOPS+ is not park adjusted-I tried to do so myself and the new rankings are at the end of the post-details tomorrow if I have time).

But after compiling that list, I tried to make an adjustment for how close the pennant race was (or wild card race). That is discussed below.

Here is the list:

Rk	Player	Year	sOPS+		Rk	Player	Year	sOPS+
1	Ted Williams	1942	348		25	Jason Thompson	1981	262
2	Barry Bonds	2001	341		26	Jimmie Foxx	1932	261
3	Hank Greenberg	1940	323		27	Ralph Kiner	1947	261
4	Ted Williams	1941	297		28	Lou Gehrig	1933	260
5	Carl Yastrzemski	1967	294		29	Rusty Staub	1969	260
6	Rogers Hornsby	1925	294		30	Stan Musial	1949	260
7	Barry Bonds	1992	291		31	Jason Giambi	2000	259
8	Babe Ruth	1920	283		32	Johnny Mize	1938	259
9	Hank Greenberg	1946	283		33	Babe Ruth	1923	257
10	Richard Hidalgo	2000	283		34	Willie Mays	1959	257
11	Bobby Thomson	1951	282		35	Jimmie Foxx	1935	257
12	Stan Spence	1944	275		36	Ron Fairly	1966	256
13	Heinie Manush	1928	274		37	Willie Mays	1955	255
14	Barry Bonds	2004	272		38	Carl Yastrzemski	1968	254
15	Babe Ruth	1927	272		39	Mark McGwire	1998	254
16	Ralph Kiner	1949	269		40	Tris Speaker	1923	253
17	Jimmie Foxx	1933	269		41	Albert Belle	1995	252
18	Rogers Hornsby	1929	266		42	John Mayberry	1972	252
19	Roy Cullenbine	1946	266		43	Miguel Cabrera	2011	252
20	Ted Williams	1939	265		44	Cy Williams	1924	251
21	Dick Wakefield	1944	264		45	Randy Winn	2005	251
22	Billy Williams	1965	264		46	Barry Bonds	2002	250
23	Eddie Mathews	1954	263		47	Harmon Killebrew	1967	250
24	Shoeless Joe Jackson	1917	262

 
So Ted Williams has the best at 348. But were the Red Sox in a tight pennant race in 1942? Not exactly. They came in 2nd, 9 games behind the Yankees. They entered September 8 games out and were never closer than 7.5 games (and that was only for one day).

So I decided to look at only guys who were on teams that entered Sept. no more than 5 games out (or ahead), were no more than 5 games out (or ahead) on Sept. 15 and finished no more than 5 games out (or ahead). That actually left Bobby Thomson of 1951 out, so then I also included any team that was no more than 5 games out (or ahead) with 5 games left.

To adjust sOPS+, I divided by the average number of games out (or ahead) per each day in Sept. and/or Oct. a team played a game. So if a team played 25 games and they were exactly 1 game out each time, they got a "closeness" score of 25/25 = 1 (a game ahead was counted the same as a game behind).

I used the average because if I am dividing, then a guy on a team that played 30 games and was 1 game out each time would have a score of 30 and it seems unfair to divide his sOPS+ by a bigger number than the guy mentioned above.

I did not take playing time into account. Maybe I should, but I am not sure what the best way would be to do so. Also, for post 1994 years, if the wild card was in play, I used games ahead or behind for that (but it got tricky since sometimes a team would be closer to the wild card leader one day but a couple of days later they were closer to the first place team in their division-I always used the lower number).

Rk	Player	Year	sOPS+	Closeness	sOPS+/Close
1	Carl Yastrzemski	1967	294	0.426	690.3
2	Harmon Killebrew	1967	250	0.367	681.8
3	Barry Bonds	2004	272	0.536	507.7
4	Hank Greenberg	1940	323	1.362	237.1
5	Barry Bonds	2001	341	1.519	224.6
6	Jason Giambi	2000	259	1.328	195.1
7	Babe Ruth	1920	283	1.593	177.7
8	Stan Musial	1949	260	1.466	177.4
9	Ron Fairly	1966	256	1.682	152.2
10	Barry Bonds	2002	250	1.750	142.9
11	Willie Mays	1959	257	1.804	142.4
12	Bobby Thomson	1951	282	3.911	72.1

Of course, Yaz and Killebrew went up against each other in 1967. Yaz played for the pennant winning Red Sox and Killebrew played for the 2nd place Twins. I gave alot of details on that season and how well these two guys did in a recent post called A Case For The 1967 American League Being The Best Season Ever 

Park adjusted ranking

Harmon Killebrew	635.24
Carl Yastrzemski	623.73
Barry Bonds	506.05
Barry Bonds	241.56
Hank Greenberg	207.79
Jason Giambi	202.62
Babe Ruth	175.94
Stan Musial	167.88
Ron Fairly	167.07
Barry Bonds	150.69
Willie Mays	148.23
Bobby Thomson	71.65

I divided sOPS+ by the park factor and multiplied by 100. I used a three year average for park factors. If a team changed it's park, then I used only 2 years, as in the case of Mays. The park factor was adjusted if a player did not play exactly half of his Sept. games at home. For some guys, it was not close to an even split. Greenberg played 22 games at home and 5 on the road. Then I divided by the closeness factor.

My closeness factor might be too linear. If one guy had 1 and another 2, that says that the first guy faced pressure that was twice as strong as the second guy. But those two cases are, in a way, pretty close. If I use the square root of the closeness factor, so that pressure increases but at a diminishing rate, here are the leaders:

Carl Yastrzemski    407.06
Harmon Killebrew    384.65
Barry Bonds    370.39
Barry Bonds    297.67
Hank Greenberg    242.51
Jason Giambi    233.46
Babe Ruth    222.03
Ron Fairly    216.66
Stan Musial    203.23
Barry Bonds    199.35
Willie Mays    199.12
Bobby Thomson    141.69

Now, Yastrzemski is a bit ahead of Harmon Killebrew. Either way, those two guys are 1-2.