Coming into the 2009 season, the Atlanta Braves’ Tommy Hanson was one of the most hyped prospects in baseball, even ranked by some above Jason Heyward.

Despite being seemingly ready for the major leagues, the Braves opted to give Hanson a taste of AAA, and left Jo-Jo Reyes in the rotation.

Instead of getting a full year of Hanson’s 2.89 ERA and 8.18 K/9, the Braves were treated to five starts of 7.00 ERA from Jo-Jo Reyes (Kris Medlen also made a couple starts, not faring much better than Reyes).

While the Braves finished six games out of the wild card race, they were in it to the end (when they lost their last six games of the year). With Hanson in the rotation all year, things could have turned out differently.

Going into 2010, the Braves faced a similar choice with Jason Heyward, who many named the top prospect in all of baseball.

Whether it was the realization of a past mistake, the need to win in Bobby Cox’s final year, to fill the stands more or because Heyward was simply the best option, the Braves decided that baseball’s hottest commodity could start the year in the MLB.

So far, it’s safe to say that Heyward has lived up to the hype. He’s got a .290/9/35 line and already has a couple walk-off hits in the bag. His on-base percentage, which stands at .414, is among the league leaders, and Heyward has shown an incredible eye at the plate.

Through 42 games, Heyward has a WAR (wins above replacement) of 1.6. This means with a replacement level player instead of Heyward, the Braves would have 1.6 less wins on the season.

But I think that it would actually be a larger difference. The two players that would have been getting more play time without Heyward around, Matt Diaz and Melky Cabrera, have a combined WAR that is less than 0 (-0.8 to be exact). That’s right; Melky and Matt Diaz have been so bad this year that they have actually cost the Braves wins.

Heyward currently leads all major league players in Win Probability Added at 3.29. That number alone makes me think Heyward should be a strong MVP candidate, not just the leader in Rookie of the Year voting.

Going further, this Atlanta Braves team feels different. With Heyward in the lineup, they are a much better team and more feared opponent. In fact, when Heyward doesn’t play the majority of the game (i.e. pinch hitting or two inning appearances as well as off days) the Braves are just 3-5, compared to 21-17 when does.

Throw in the fact that a large portion of the attendance increase at Turner Field is likely due to Heyward, and he is helping the organization on and off the field.

All in all, I think that the Braves decision to start Heyward in the majors has been huge. I would give the Braves a record of 21-25 (as supposed to 24-22) without Heyward on the team. If the Braves called Heyward up at the same time as Tommy Hanson, I think the Braves team is worse by at least 4 games, which likely determines whether the Braves will play or watch in October.

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