The Player of the Year will be announced during the hour-long 2015 Players Choice Awards show on MLB Network, Monday at 8 p.m. ET. The program will be presented by MLB The Show™ and sponsored by Majestic Athletic.
The Players Choice Awards, in which the players recognize each other's excellence on and off the field, have been presented by the Major League Baseball Players Association since 1992, with the Players Trust providing more than $4 million in charitable grants to causes selected by the winning players.
The Player of the Year winner will receive a $50,000 grant from the Trust that will go to a charity or charities he selects.
Donaldson, a 29-year-old in just his third full season, batted .297 with 41 home runs and also led the league in runs (122), RBIs (123), total bases (352) and sacrifice flies (10). He also led the Major Leagues with 20 game-winning RBIs to help Blue Jays win the AL East.
In his 12th season and third with the Dodgers, Greinke, 32, was better than ever, going 19-3 with 200 strikeouts in 222 2/3 innings while leading the Majors with a 1.66 ERA, a 9.3 WAR, 0.84 WHIP and a .231 on-base percentage allowed.
Harper, who was the first overall pick in the 2010 First-Year Player Draft and who reached the Majors two years later at age 19, had a breakout season for the Nationals in 2015, batting .330 with a league-leading 42 homers and 99 RBIs, and leading the majors in on-base percentage (.460), slugging percentage (.649), OPS (1.109) and WAR (9.9). He also had 38 doubles and 124 walks.
The winners and finalists for each award were selected by players Sept. 16 in league-wide balloting conducted under the supervision of accounting firm KPMG.