All other things being fairly equal, it would be fine to go with the 'hot hand'. However, if you have a guy like Mookie in an 0 for 30 slump versus someone like Holt who is 15 for his last 30, it would be a mistake, IMO, to go with Holt. That might be an extreme case, but the point is, you go with the better hitter over the 'hot' but weaker hitter.