Andy Pettitte's back! What does it mean?

Well, this season just got even more interesting with the announcement that Andy Pettitte will be returning to the New York Yankees.

The cynic would suggest that maybe the New York Yankees are worried about Michael Pineda's velocity. The reality is undoubtedly more simple: A Yankee legend wanted to return. The Yankees, of course, have nothing to lose except a $2.5 million investment.

But will this be an upgrade in the rotation? Obviously, once Pettitte is stretched out -- maybe mid-April -- he's in the rotation, which bumps somebody. Here are the ZiPS projections for the rotation candidates:

CC Sabathia: 3.55

Michael Pineda: 4.11

Hiroki Kuroda: 4.33

Ivan Nova: 4.44

Phil Hughes: 4.84

Freddy Garcia: 4.85

Pettite was very good with the Yankees in 2010, posting a 3.28 ERA over 21 starts. That was actually his best ERA in years; from 2006 through 2009 he posted a 4.24 ERA with the Astros and Yankees, a figure that made him only slightly better than a league-average pitcher. Pettitte was never really a great pitcher, was more of a consistent and durable winner. Pettitte's skill-set didn't suddenly improve in 2010; basically, he stranded more runners and had a better defense behind him, leading to fewer base hits. Here are his fielding independent ERAs each season:

2006: 4.13

2007: 3.87

2008: 3.71

2009: 4.15

2010: 3.85

So he was really the same guy all those years, with the only blip being the tender elbow that sidelined him from mid-July to mid-September in 2010. Pettitte returned and pitched well, including allowing just four runs over 14 playoff innings.

But will he be the same pitcher in 2012? Pettitte's now 40 years old. What happens to pitchers at that age? Over the past 25 years, there have been 19 40-year-old pitchers who pitched at least 150 innings.

  • Fifteen of the 19 posted an ERA+ of league average or better. This makes sense; only good pitchers are still around at age 40 and old pitchers are going to be on a short leash if they're not any good. So if an old pitcher remains in the rotation it's because he's at least decent. I suspect this would be the case with Pettitte; he's either the same as he's always been or gets shelled over a few starts and hangs 'em up again.

  • Collectively, the 19 pitchers posted a 3.76 ERA at age 40 ... and a 3.85 ERA at 38. They actually pitched more innings at age 40 -- 3788.1 to 3540.2. Of course, none of them missed an entire season at age 39. Again, this would seem to confirm the above statement: If Pettitte remains reasonably healthy, he should be the old Andy Pettitte.

  • Eleven of the 19 had a better ERA+ at age 40 than age 38, although the margins were very close in some cases. The only pitcher with a significant drop from his age-38 ERA to age 40 was Orlando Hernandez, who posted a 3.30 ERA in 15 starts with the Yankees in 2004 but a 4.66 ERA in 29 starts with the Diamondbacks and Mets in 2006.

So we can assume Pettitte should be capable of posting an ERA around 4.00. This would likely be a minor upgrade over the team's current fifth starter, Hughes or Garcia. For all the hype around Hughes, he's had one good season in the rotation and it wasn't that dominant, with a 4.19 ERA in 2010. And even in that it was only two good months (April and May). His ERA over the final four months that year was 4.89. Certainly, Pineda could also be sent down to the minors if he continues to throw 90-92 mph instead of the 95-98 he fired with the Mariners a season ago.

In the end, it gives them more depth than anything. There's never anything wrong with that.