AaronGleeman.com

I spent much of the offseason criticizing the Twins for signing Kevin Correia to a two-year, $10 million contract, wondering why a 32-year-old with such an underwhelming track record was their target in the first place and why they felt the need to make him a two-year commitment at a time when similarly mediocre starters were signing one-year deals all over the place. And now a month into the season Correia has a 2.23 ERA while going at least seven innings in all five starts.

On this week's "Gleeman and The Geek" episode we talked at length about the extent to which everyone but the Twins have been wrong about Correia so far and I certainly wouldn't begrudge anyone for piling on further, but I also thought it would be worthwhile to delve a little deeper into exactly how he's out-performed expectations. First, let's take a look at which pitches he's thrown and how often he's thrown them, as classified by PitchFX:

             2013    2012    2011
Fastball      13%     25%     27%
Sinker        24%     24%     25%
Cutter        35%     28%     28%
Curveball     12%     12%     12%
Changeup      16%     12%      8%

Pitch classifications are always tricky and in Correia's case what PitchFX is calling a "changeup" is actually what he calls a split-fingered fastball. And he's throwing that pitch a whole lot more often this season while significantly reducing his four-seam fastball usage. That's a conscious change to his approach and at first glance it's changed his results too, but let's go beyond ERA to examine how his 2013 numbers compare to his 2010-2012 numbers:

            SO%     BB%    BABIP      GB%     LOB%      HR%     xFIP
2013       10.6     3.5     .271     46.7     82.9      4.8     4.17
2010-12    13.8     7.3     .293     48.5     68.7     13.0     4.26

Part of why I disliked the Correia signing so much was that he had one of MLB's lowest strikeout rates from 2010-2012 at 13.8 percent (or 5.4 per nine innings). This year Correia's strikeout rate has actually dipped even lower to 10.6 percent (or 3.7 per nine innings), which is a decrease of 23 percent when broken down per plate appearance. To put that in some context, last year only one MLB starter had a strikeout rate below 11 percent and Max Scherzer led MLB at 29.4 percent.

Correia's strikeout rate has gone from bad to worse, but he's dramatically improved his walk rate. Despite pitching to so much contact he never had particularly good control, walking 3.5 per nine innings from 2010-2012 and never walking fewer than 2.4 per nine innings in a season. This year he's walked 1.2 per nine innings, which is an improvement of 52 percent per plate appearance. For context, strike-throwing machine Brad Radke's career walk rate was 1.6 per nine innings.

My perception of Correia's first five starts was that he induced a ton of ground balls, but in reality his ground-ball rate of 46.7 percent is around league average and below his rate of 48.5 percent from 2010-2012. So if his already awful strikeout rate has declined 23 percent and he's inducing fewer ground balls, how is Correia thriving? Improving his walk rate from mediocre to spectacular shouldn't be overlooked and leaning on the splitter has helped him against left-handed hitters.

Beyond that, however, he's been pretty fortunate/lucky. Correia's batting average on balls in play is .271, which is 22 points below his 2010-2012 mark and 19 points below MLB average. Of the runners he's put on base 82.9 percent have been stranded, compared to his 2010-2012 mark of 68.7 percent and the MLB average of 72.9 percent. And last but definitely not least, Correia has allowed a homer on 4.8 percent of his fly balls, compared to 13.0 percent from 2010-2012.

Giving up just two homers in 36.1 innings goes a long way toward making up for any weaknesses in other areas and Correia has definitely gotten away with some close calls on a handful of deep, well-struck fly balls that were hauled in on the warning track. And close calls or not, 4.8 percent simply isn't a sustainable rate of homers per fly ball. MLB average is 10 percent and his career mark is 10.6 percent, so going forward his home run rate can roughly be expected to double.

Making half his starts at Target Field will certainly help suppress Correia's homers, but he's called pitcher-friendly ballparks home for most of his career--including Petco Park in San Diego, which is the pitcher-friendly ballpark--and still had a typical rate. And despite having Target Field on their side Twins pitchers as a whole had a home run rate of 10.4 percent from 2010-2012, so at some point the ballpark can only do so much.

Advanced metrics like Expected Fielding Independent Pitching (xFIP) take into account what the norms are for rates like batting average on balls in play, left-on-base percentage, and home runs per fly ball in an effort to show what a pitcher's ERA would look like if luck/good fortunate weren't a factor. Correia had a 4.26 xFIP from 2010-2012, including 4.34 last season. Through five starts this season his xFIP is 4.17.

It's also worth noting that Correia has gotten off to strong starts in past years only to end up with mediocre overall numbers. In fact, if you take his first five starts in each of 2010, 2011, and 2012 he had a 3.59 ERA in 90 innings. From his sixth start on in those three seasons Correia had a 5.04 ERA in 380 innings. That's not meant to show anything about Correia specifically so much as it's meant to say five starts are only five starts and April is only April.

There's no doubt that Correia has looked very good so far and if his improved control is here to stay that would be a big factor in his potential improvement, but for the most part the underlying factors within his performance are much closer to his career-long mediocrity than the nice-looking 2.23 ERA would suggest. None of which means his good fortunate/luck is guaranteed to change for the worse, but given how Correia has pitched things evening out would be bad news.

This week's blog content is sponsored by "Hank Greenberg: The Hero of Heroes" author John Rosengren's upcoming appearance at the Minneapolis Sabes JCC on May 5. Please support him for supporting AG.com.