The backup catchers almost certainly won't get used. And yesterday's starting pitchers won't either. The Giants burned Machi, Strickland, and Vogelson yesterday to save their better pen arms -- highly unlikely we'll see any of those guys. KC had no bullpen guy throw more than 1 IP yesterday, and the day before that was an off-day, so theoretically those guys could go tonight but they're at the bottom of the depth chart. So 20 for SF and 23 for KC are the upper limit. Unless the starters are really dealing (which seems unlikely, since it's both teams' 4th starters), the hooks will be very quick and a lot of pitchers will be used. You do however get fewer guys in the game in the AL without the need for pinch hitters and double switches and so on.