It's the first rookie honor for the 26-year-old, who compensated for a .257 September average with a massive power surge. Cespedes led AL rookies with seven home runs, 19 RBIs and a .532 slugging percentage during the month. He also tied for first with five doubles and two triples and tied for second with 18 runs scored.
The surge began on Sept. 11, when Cespedes snapped a 21-game homerless streak by going deep against the AL West-rival Angels. He also homered in two of the next three games, wins over the Angels and Orioles.
Cespedes capped the month on Sunday, when he went 3-for-4 and finished a double shy of the cycle, as the A's beat the Mariners a day before clinching a playoff berth.
For the season, Cespedes ranks second among AL rookies in most statistical categories, including on-base percentage (.352), slugging percentage (.506), home runs (23) and RBIs (82).
Andrew Simon is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.