Mike Trout and Bryce Harper have had historic rookie seasons, but the highly touted prospects were expected to play at this level -- although maybe not this early in their careers. Here's a list of the top breakout seasons that were less expected:
5. RF Josh Reddick, Athletics »
The 25-year-old has been the A's much-needed power bat in the middle of their lineup for their surprise playoff push. The former Red Sox prospect has a team-high 29 home runs and 79 RBIs.
4. 1B Edwin Encarnacion, Blue Jays » In his eighth season in the league, Encarnacion has set career highs in home runs (40) and RBIs (102). The power surge also led to a contract extension in July.
3. SP Chris Sale, White Sox »
He has gone from a bullpen option in 2010 to a Cy Young candidate in 2012. In his first season as a starter, Sale is 17-7 with a 2.82 ERA and 181 strikeouts -- ranking in the top six in the AL in all three categories.
2. 3B Chase Headley, Padres » No NL player has been hotter since the All-Star break. Headley leads the league in home runs (20) and RBIs (62) while batting .307 since July 13. The 28-year-old has inserted himself in the NL MVP discussion.
1. SP Kris Medlen, Braves » The 26-year-old has been unbeatable -- literally. After losing the first two starts of his career in 2009, he hasn't taken a loss in 26 since, and the Braves have won the last 21 of them. The right-hander began the 2012 season in the bullpen before Atlanta added him to the starting rotation July 31. Since then he is 8-0 with a 0.76 ERA in 10 starts.
- Jeffrey Tomik