Ryan Howard, 58, 2006
After homering 22 times in 88 games en route to NL Rookie of the Year honors in 2005, Howard began 2006 with an Opening Day homer against the Cardinals, but he hit just five for the month. He reached 20 homers in the season's 57th game, had 28 through 81 games and after hitting three in a game against the Braves on Sept. 3, he had 52 in 136 games. Though he added four in the five games after that, pushing him to 56 in 141 games, he hit just two over the final 21 games. Still, his total of 58 stands as the highest since Barry Bonds' 73 in 2001.