Nate Silver From Baseball Prospectus: A-Rod Not a Lock to Become HR King

Sometimes Baseball Prospectus is a little much for me with their complicated statistical analyses, but if anything they definitely provide food for thought for diamond dorks like me.

In Silver's latest work for BP, he argues that while it seems like a foregone conclusion for most that Alex Rodriguez will break baseball all-time home run record, some indicators would argue it's not.

Silver's reasoning against A-Rod hitting the final 210 home runs to pass Barry Bonds is as follows:  (and FYI, at Rodriguez's current pace, he'd break the all-time home run record at the tail end of the 2013 season)

1. According to the aging curve, which evaluates players statistics based on age, the biggest point of decline comes between ages 32 and 34.  A-Rod turns 33 this season.  And consider these numbers he points out:  In 2007, A-Rod hit 30 dingers in the first half of the season, and just 24 in the second half.  Last year, he hit 19 homers in the first half and just 16 after the break.  Those numbers would coincide with the statistical analysis, and could suggest he'll continue to decline.  Silver does point out, however, "that could be just a fluke."
2. A-Rod has never suffered a significant injury, that is, until last season when he missed 24 games.  He hadn't missed that many games in a season in 10 seasons, as his last significant sidelining came in 1999.  Silver points out that players who have taken steroids are more prone to injuries, and when a player reaches his mid-30s "injury problems sometimes can be compounding".
3. Based on a statistical analysis called PECOTA, which "stands for Player Empirical Comparison and Optimization Test Algorithm, projects player performance based on comparison with thousands of historical player-seasons, analyzes similarities with past player-seasons based not only on rate statistics, but also height, weight, age and many other factors", according to BP's website, A-Rod will significantly decline from here on out.  Silver argues that based on the 20 most comparable players to A-Rod, and this statistical analysis, A-Rod will hit 730 home runs if he retires in 2019.  He'll hit 33 home runs next year, 30 the year after, and then decline incrementally year after year until he hits one measly dinger in 2019 to finish 32 home runs behind Barry Bonds.

On the other hand, Silver acknowledges there are other factors indicating A-Rod does have a great shot to break Bonds' record:  He's a great athlete, he will earn $30 million in bonuses for every player he passes in pursuit of the record, and based on stats, players who start their careers in a flourish tend to finish them the same way.  So the fan perception that breaking the record is a formality may actually become a reality.

Pretty interesting huh?  Check out the entire article here.