Rookies normally don't impact the league in a major way in baseball, but 2015 is a special year, because these guys are playing a pivotal force in the outcome of the season.
While many first year guys are playing great baseball right now, none are performing to the level of Kris Bryant. Taking into account his stats and the turnaround of this team in his first year, Kris Bryant is my choice as the best rookie in baseball.
With 20ish games left to go, Bryant is posting a chunky stateline of 267 BA with 23 homeruns and 86 RBI.
The Cubs were one of the worst teams in baseball over the past decade or so. This team looks energized for the first time in a LONG time. You have to also take into account that Bryant plays third base, which is one of the hardest positions in baseball. With the right off-season plan, KB could become a 285, 30HR, 110RBI guy as soon as next year, and maybe an MVP candidate in the next three.