Harper stated. He went 0-for-1 with a strikeout and a walk. Harper struggled in the games following the All-Star break, hitting .176 with 26 strikeouts in his first 116 plate appearances in the second half of the season. Manager Davey Johnson began to give Harper days off due to his poor play and visible on-field frustration. Johnson said that Harper had become "overly aggressive" at the plate. Harper's play began to improve in late August. He hit two home runs in a game against the Miami Marlins on August 29, his first career multi-homer game, and received his first major league ejection after throwing his helmet down in the ninth inning in response to hitting into a double play. He had a second multi-homer game on September 5, against the Chicago Cubs. Harper was named Rookie of the Month again in September after hitting .330 with seven home runs. Harper's 254 total bases and 57 extra base hits were the most ever for a player under age 20, while his 22 home runs, 98 runs scored, .340 on-base percentage, .477 slugging percentage, and .817 on base-plus-slugging were the best regular season totals for a teenager in the past 45 years. In Game 5 of the 2012 NLDS against the St. Louis Cardinals, Harper hit his first postseason home run. The Nationals would eventually lose the game 7–9 despite leading by 6 runs. He finished his first postseason appearance with a .130 batting average. Harper was named the National League Rookie of the Year. He received 112 votes, 16 of them first-place votes, beating Arizona's Wade Miley (105 votes, 12 first-place) and Cincinnati's Todd Frazier. 2013 season Harper hit two home runs against the Miami Marlins on Opening Day of the 2013 season. At age 20, he became the youngest major league player to hit two home runs in his team's first game of the season. He was voted a starter for the MLB All-Star Game, his second career All-Star selection. After hitting 13 home runs in just 58 games, Harper was selected to participate in the 2013 Home Run Derby. Harper hit a total of 16 home runs in the first two rounds to advance to the final round, in which he faced Yoenis Céspedes, an outfielder for the Oakland Athletics. Although he lost 9–8 in the finals, Harper was the second-youngest player to participate in the Home Run Derby,