I am a White Sox fan, and have often wondered the same thing about comiskey park. While the circles to which i am fairly sure you are referring are rather close to the plate, i have always felt that they were supposed to be some sort of "novelty" on deck circles. The players in actuality warm up while on deck just outside the dugout on the plate side. There (at least on the home side, I have never sat close enough on the visitor's side) is some sort of mat (that is, I do not believe it is anything permanent, just something lain down) with the sox logo on it, that is just about the same size as the circles near the plate. This leads me to believe that maybe in the past the circles near the plate were used for on deck batters, but that practice was stopped when they realized it was too dangerous. Perhaps, this realization came before Comiskey Park (II) was built in '90 (maybe '91?), but they decided to keep the circles as a similarity between old and new comiskey (hey, it could happen....they shipped the infield dirt from old comiskey to put it in new comiskey).
Also, if I remember correctly, they might put decorative mats or something down on those circles during games of high importance (playoffs, although that is so rare for the sox, and they may do it next year for the all star game). This however, is something I am not confident on. Not to say that I am confident on the first part of my post, just my completely uneducated guess.
|