Would re-signing Joe Nathan be a good idea for Twins?

The Twins announced on Tuesday that they have officially declined the $12.5 million option on Joe Nathan for 2012. Yet, according to general manager Bill Smith, Nathan remains a very viable candidate to return to the team for 2012, only on a lesser salary:

"I spoke with Joe and his agent this morning, and expressed our interest in re-signing [him]. We will remain in contact with them as we move forward into the free-agent process.”

In the TwinsCentric Offseason GM Handbook, we noted that the closer free agent pool is littered with similar arms to Nathan and we pegged his as the fifth-best among right-handed closers on the market. We estimated that his contract would be approximately two-years, $14 million – a very reasonable rate given his performance record, age and injury history. The question is: Would that be a good investment for the Twins?

Yes, Nathan came back a bit prematurely last year and was cuffed around (a fact that was definitely predicted). From April through May, he worked 15.1 innings, allowed 15 runs on 17 hits and posted a sad 15/9 K/BB ratio. In that time he received swinging strikes on another 8%. That figure was particularly disheartening considering the lowest rate he held since converting to a closer with the Twins was a 12% swinging strike rate.

Because of these results, he went on the DL and then the Twins sent him to Rochester to try to work through some stuff. ESPN1500’s Phil Mackey reported that during his time with the minor league club, Nathan was able to work through some scar tissue that had formed on his elbow, providing him with a great range of motion in his throwing arm. After breaking up the scar tissue, Nathan’s season got back on track. In his final 31 appearances, he worked 29.1 innings allowing only 11 runs and held a significantly better 28/5 K/BB ratio coupled with an opponent average of .193 (not to mention, 11 saves in 12 opportunities). What’s more is that in the season’s final two months, he had increased his swinging strike rate to 11%.

Thanks to dissipated scar tissue, Nathan was able to turn his season around. First, he was able to regain velocity on his fastball:

Joe Nathan’s 2011 Fastball Velocity
Month	Miles Per Hour
March/April	91.3
May	91.7
June	92.6
July	93.0
August	93.3
September/October	91.9

 (via Fangraphs.com)

As you can see, Nathan peaked a bit in August before losing some heat on his fastball. This is perfectly normal. Due to it being his first year back since 2009 as well as the natural bell-curve effect of pitcher’s seasonal velocities, a decline at the end of the season is not unexpected. Still, the improvement in not only his velocity but also his fastball’s effectiveness in the second-half of the year was impressive.

Since he no longer had the build-up on his elbow restricting his motion, Nathan was able to spin his slider – arguably his best pitch – better in the latter portion of the year. 

In the first-half of the season, he struggled to locate the pitch where he wanted it. You can see that visually here:

This scatterplot of sliders resulted in a whiff rate of 13.3% on this pitch. Comparatively, this was a pitch that held a 21.3% whiff rate from 2008 to 2009. Clearly, lacking his velocity combined with a substandard slider, opponents were able to tee up on the pitches they liked instead of fishing for a slider darting out of the strike zone or a fastball above it.

Following his recovery in Rochester, Nathan returned with a much more lethal slider. Over the course of the next few months, he increased his whiff rate to 24.6% while spotting his slider down-and-away from right-handed hitters:

This improved secondary offering complemented his jazzed up fastball which changed hitter’s line of vision much better than in the season’s first-half. The results were more strikeouts and less solid contact.

At 37 years old in 2012, he’s no spring chicken but the progress he made in final three months of 2011 signifies that he is certainly capable of holding down the backend of the Twins bullpen for the next two seasons.