I've often wondered how much time they spend "working on things" once the season starts. Look, I'm not suggesting that we shed any tears for MLB players but at the same time their "job" is demanding both physically and time-wise. They're expected to show up at the field 4 hours before game time and don't leave until an hour after the game is over. During that time they have to get dressed (leisurely, I'm sure!) have their BP, share the field with the visiting team, and have the field vacated in time for the grounds crew to get the field ready for play.
These guys are professionals and they've played hundreds of games and spent thousands of hours practicing by the time they get to this level. IMO they know what to do in just about any situation. It's the function of the coaches to remind them of those things.
IMO the Field Manager's primary purpose isn't to handle in-game situations as much as it is to run the clubhouse. He has 25 players with 25 egos in the clubhouse at any given time, and s*** happens. Being field manager is secondary to trying to the clubhouse issues. I agree completely with cp in that for the Field Manager it's all about establishing expectations, demanding those expectations be met, and motivating. Tito was an excellent on-field manager and handled the bullpen well, but it was losing the clubhouse that led to his departure.