Is Age to Blame for Joe Nathan’s Decline? by Chris Cwik September 3, 2014 Tigers closer Joe Nathan hasn’t had the type of season fantasy owners were expecting. While Nathan has notched 32 saves, things haven’t come easy. Through 50 innings, Nathan has a 5.04 ERA. The performance has been somewhat of a shock. Yes, there were some reasons to be concerned about Nathan entering the year, but it’s safe to say no one expected him to struggle this much. One of the main reasons for concern entering the season was Nathan’s age. It’s tough for any player to be dominant at age-39. Are Nathan’s struggles a product of his age, or is there more going on here? It would be irresponsible to write off all of Nathan’s issues on his age, even though there’s a good chance it has played a role in his decline. In January, I looked at other valuable relievers entering their age-39 seasons, and found that most of them, even the elite ones, fell off quite a bit at age-39. At the time, though, it was tough to imagine Nathan dropping off so precipitously. Sure, regression was expected after he posted a 1.39 ERA, but his peripherals seemed manageable. Though I predicted there would be some decline due to age, I didn’t expect this. While my initial article looked at one thing, a player’s age, in order to determine whether Nathan would perform well, that’s obviously a simplistic view of things. Every player is different, and not all players, or relievers, are doomed at age-39. This season, both Koji Uehara and Jamey Wright have posted solid numbers despite being the same age as Nathan. We’re not breaking new ground here by saying all players are different, but it’s worth stressing that age hasn’t stopped those two players. So, what has led to Nathan’s decline? A quick look at his .326 BABIP might suggest regression is coming, but that may not be the case. Nathan has proved to be a lot more hittable this season. A big part of that is likely due to his declining fastball. Nathan’s average fastball is down from 93.20 mph last season to 92.85 mph this year. Declining velocity has been a trend for Nathan, and was evident last season. People weren’t quick to notice Nathan’s poor velocity last season due to his strong results. The difference this season is that his fastball isn’t fooling hitters anymore. Despite the drop in velocity last season, Nathan’s fastball still had a PITCHf/x pitch value of 9.1. This season, it’s registered as barely above replacement level with a 0.7 pitch value. To combat the drop last year, Nathan started relying on his slider more. It turned into an incredible weapon for him. That hasn’t been the case this year. Nathan’s not getting the same results with the pitch anymore. He’s still getting whiffs with the pitch at a solid rate, but he hasn’t been able to hit the strike zone as often. Nathan’s ball% with his slider has jumped from 33.51% last year to 40.84% this season. Nathan’s sinker has seen a similar rise in ball% this season. His inability to control both pitches is probably one of the reasons Nathan’s walk rate has jumped to 11.3%. We can’t really be certain how much of those issues are related to age. It’s conceivable to blame Nathan’s declining fastball on age-related issues, but we can’t say with certainty that his age is to blame for his sudden loss of control. Both issues have played a big role in his downfall this season. While it doesn’t necessarily help that Nathan is 39 years old, it’s not like he’s giving himself a chance to succeed with his poor control.