When thinking about how a player is projected to play, it would be a mistake to think of it as a single number, frozen in time. Projecting baseball players (and other things) is an inexact science, one in which we make very educated guesses about a midpoint of a player's likely performance and hope that reality resembles our projection. When the games actually start, all that new information is relevant and our projections must change. If a player we think is a .250 hitter hits .350 for six weeks, that doesn't mean that we suddenly believe he's a .350 hitter, but it does make it more likely that we were wrong and he's a .260 hitter and less likely that he's a .240 hitter.
The ZiPS projection system incorporates the daily round of games into the previous history of the player in order to make new estimates of a player's production going forward. In most cases, these new estimates will be very close to the preseason projection. For example, Mike Trout and Miguel Cabrera have thus far had relatively weak seasons -- for them -- but their new projections going forward are only a hair lower than they were in March. That's not true for everybody, however.
Below are 10 of the players who have seen the greatest increase or decrease in rest-of-season projections.
Tulowitzki was already a bonafide superstar coming into the season, but he's been on another level of reality this year, hitting .389/.492/.757 with 13 homers. If Tulo gets hits by a bus tomorrow, he's already had an All-Star level 2014 season as a whole, regardless of whether you prefer Baseball Reference's WAR interpretation (4.4 WAR) or that of FanGraphs (4.1).