Posey was tied with Heyward for fifth among NL rookies with 18 home runs, and was fourth with 67 RBI in just 108 games. He finished first with a .305 batting average and a .505 slugging percentage and ran the best pitching staff in the major leagues.
Posey is the sixth Giant to win the NL Rookie of the Year, a list that includes three Hall of Famers. He is also the fifth San Francisco Giants rookie to finish the season with a .300 batting average and double-digit home runs.
Three of the other four also won the award, and the other lost out to his teammate who accomplished the same feat in the same season.
Heyward had one of the best seasons for a player as young as he is (he turned 21 during the season) in a long time. While Posey has a significant edge on Jason Heyward in both batting average and slugging percentage, there is one next-level metric in which Heyward has a decisive edge.
Win Probability Added measures the value of every plate appearance during a given season, and how much it contributes to a team’s chances to win. For example, in a tie game, with no one on base and one out in the top of the ninth inning, a player hits a go-ahead home run.
He took his team’s chance of winning (based on historical data) from 43 percent to 80 percent, so he gets a credit of 37 percent. Win Probability Added sums a player’s credits (and debits) over a season to get their total value.
Heyward had a LOT of big hits for the Braves this season, so many that he ended the season ranked sixth-best in the NL with a WPA of 4.82 wins (his offensive contributions were worth 4.82 wins). That dwarfs Posey’s 1.09 WPA, which admittedly is hurt by his only playing 108 games, but is unlikely to have been anywhere near Heyward’s had he played the full season.
Jaime Garcia finished third after going 13-8 with a 2.70 ERA for the St. Louis Cardinals. His 13 wins led NL rookies (only one other pitcher had 10) and his 2.70 ERA was second among rookies with a minimum of 81 innings pitched.
And Gaby Sanchez of the Florida Marlins finished fourth, after leading all NL rookies with 85 RBI and hitting 19 home runs, which was tied for third.
With Neftali Feliz winning in the American League, the Rookies of the Year faced each other in the World Series for just the third time in baseball history. In 1981, the New York Yankees and Dave Righetti faced Fernando Valenzuela and the Los Angeles Dodgers. And in 1951, Gil McDougald and the Yankees faced the New York Giants and Willie Mays.