At 38 years old, Derek Jeter led all of baseball with 216 hits, 11 more than the MVP winner Miguel Cabrera. He hit .316/.362/.429 with a 117 wRC+ and 15 home runs. All of this happened after two seasons where his offense could barely pass as average, even for a shortstop. 2012 wasn't a huge surprise though, since Jeter entered the second half of the 2011 season as a whole new player with a quality swing we hadn't seen in years, but questions remain whether or not the right hander can maintain this level of offensive production while staring down his 39th birthday in 2013.
In 2012, Jeter's batted ball rates showed a significant return to his career rates. In 2010 and early 2011, Jeter's low line drive rates were a clear factor in what we believed was age regression, but for the last year and a half, Jeter's line drive rates have jumped from mid-teens to the low-20's. This mark is consistent with his career line drive rate, but a 62.5% groundball rate in 2012 is a 4.5% increase from his average, likely a factor that could continue as he ages. This is a trend that began in 2010 and hasn't stopped, but fortunately, Jeter has maintained good numbers on these hits. In 2012, he batted .249 on groundballs, which isn't far off from his career .258 average.
As his groundballs have increased, Jeter will have to maintain decent speed out of the batter's box to continue to see this sort of batting average. With the ankle injury he suffered in last year's postseason, as well as his declining range on the field, Jeter's legs are beginning to show signs of possible age-related health problems. Assuming he can stay on the field, Jeter is going to have to keep his legs in good shape if he wants to beat out the groundballs that he puts into play more than 60% of the time.
But Jeter's physical fitness has always been exemplary. The fact that he's remained so productive as an offensive player at the age of 38, despite playing over 2500 major league games at short stop, should show fans how well he has maintained his body. According to FanGraphs, only Luis Aparicio and Omar Vizquel played more career innings at short stop than Jeter, and by the end of 2013, he'll likely have the most. He's entered uncharted waters when it comes to his age and use, and age will catch up to him eventually.
Fortunately, outside of his age there aren't many numbers that indicate decline. In terms of value, fWAR had him at 3.2 wins in 2012, but I believe this number might even increase in 2013. His negative range in 2012 was at such a low extreme for his career that you'd expect him to improve drastically on it. Although it's unlikely that his range even touches baseball's average, his -16.4 UZR/150 in 2012 was almost 10 full points below his career -6.5, and much lower compared to his -8.8 in 2011 and -5.4 in 2010. Even with an injury and age regression, Jeter should see his UZR increase substantially, and likewise see his WAR jump. This doesn't mean that he'll be more valuable in 2013, as UZR is often flawed within such a low sample size.
Overall, nothing says that Jeter was lucky in 2012, but it's hard to imagine that he'll be able to maintain his offense with the mileage on his legs. A lot of his hits are products of groundballs, and if his legs don't hold up, we're bound to see major batting average declines. But in the end it's almost impossible to judge a player that's already defeated age to this point. Only time will tell when Jeter's days are numbered, but a betting man would expect regression.