While watching the Ranger's broadcast of their game vs. the White Sox last night, one of the announcers said something about how Josh Hamilton's HRs are usually very important, like the one that put them ahead 2-1. Then he said something about Sammy Sosa like "in those years when he was hitting 60 HRs, he alot of them when the game was one sided."
I don't know if that is true. Here is one way to look at it. Sosa had a HR% in non-close and late situations of 10.12% during these years. In close and late (CL) situations, it was 8.85% (so he dropped off, but that is still much higher than most players in CL situations). But hitters generally have a lower HR% in CL situations. From 1991-2000, it was 2.99% in non-CL cases and 2.63 in CL situations, for a decline of about .0036.
So let's suppose that Sosa's differential should have been only .0036, then he should have had a 9.76 HR% in CL situations. He had 384 CL ABs. A 9.76 HR% would give him 37.47 HRs in CL situations. He actually had 34. So maybe he should have had 3.47 More HRs in those years, if he had not "choked" in the clutch. This is not a big deal.
Conversely, if we add .0036 to his .0885 CL HR% to get his expected non-CL HR%, we would have a HR% of 9.21%. In his 2,165 non-CL ABs, he would hit 199 HRs. He actually hit 219 in non-CL situations during those years. If we take away 20 HRs over these four years, he ends up with 233 instead of 253. That is still an average of 58.25 per season. Pretty incredible.
But we can easily imagine that Sosa had to face some very tough relievers in those CL situations, who might have been told to not give him much to hit. The following table summarizes his stats in various situations in each of the four seasons. Sept and Oct data are shown for 1998 & 2001 because in those years the Cubs were fighting for a playoff spot. In general, I think the numbers show that he hit very well with runners on or in CL situations or late in the season when the Cubs were trying to make the post season (they finished last in both 1999 & 2000). Sosa hit alot of meanigful HRs in these years. There is nothing misleading or deceiving about his performance or his stats.
To see what the normal clutch/non-clutch differentials are, go to General Clutch Data.