Can We Explain the Volatility of St. Louis Cardinals Reliever Marc Rzepczynski?

Last season's multi-player trade between the St. Louis Cardinals and Toronto Blue Jays will forever be remembered for the polarizing center field talent that was shipped from St. Louis to Canada. In return, the Cardinals received a starter, right-handed reliever, and bench outfielder, each of whom was under contract through only the end of the 2011 season. Because he was the only player under St. Louis control after the last out of the season, Marc Rzepczynski was the centerpiece of the Rasmus trade for the Cardinals.

Rzepczynski was an intriguing acquisition and not just because of his alphabet soup last name that inspired the wonderful nickname of "Scrabble." The southpaw had started for the Blue Jays and pitched in relief. In 2009 and 2010, Rzepczynski started 23 games for Toronto in the American League East, facing the brutal combination of lineups featuring a DH, hitter-friendly ballparks, and high-payroll offensive juggernauts. In those 23 starts, Rzepczynski threw 124 innings, struck out an impressive 8.27 batters per nine innings, but walked 4.35 per nine and had a K/BB ratio of 1.90 because of it. Even though his 4.39 FIP in that hitter-friendly environment was nothing to sneeze at, Toronto shifted him to the bullpen, where he experienced success.

For the 2011 Cardinals, Rzepczynski presented a bullpen option who was nasty versus left-handed batters and could also be trusted to face righties. At the time of the trade, Rzepczynski had posted a decent 7.55 K/9 and 3.43 BB/9; his 2.97 ERA was good for a 73 ERA- even as his 3.83 FIP was a not-quite-as-excellent-but-still-quite-good 83 FIP-. Rzepczynski's 2011 line with Toronto was an unquestionable upgrade from the lefties the Cards had deployed in the four months prior to the trade.

As DanUp refreshingly pointed out earlier this season, small sample size performances are to be celebrated. That being so, Rzepczynski's 2011 in The Birds On Bat deserves a cake and party favors. Scrabble outperformed fans' wildest expectations, becoming an overpowering weapon for manager Tony La Russa during the club's improbable run to end the regular season and win the World Series.

After allowing three runs in the club's 11-7 loss to the Phillies in Game 1 of the NLDS, Rzepczynski allowed one run and four hits in 9 1/3 postseason innings while striking out nine opposing batters to just one walk. In recognition of the trade and celebration of Rzepczynski's wonderful nickname, my in-game snack of choice switched from Colby cheese flavored Cheez-Its to Scrabble Cheez-Its. During the NLCS, I'd race to the pantry for the crackers whenever La Russa brought Scrabble into the game. The ritual worked (in my mind) as Rzepczynski was particularly effective when called upon after the postseason's first game.

After 31 innings of Rzepczynski's nasty swing-and-miss outings in which he struck out a ton of batters, I was sold. Visions of the Cardinals having their Sean Marshall type of lefty in the bullpen were dancing in my head. In my notebook of possible VEB post subjects, I scribbled "Scrabble is the Cards' Marshall" as an idea for midseason 2012. My fanciful hopes for Scrabble rested on the shaky foundation of a small sample size that would crumble via the volatility of reliever performance.

On May 16, 2012, Rzepczynski had thrown 13 2/3 innings with the type of line the Cards had likely expected from their incumbent southpaw: nine strikeouts to two walks with a 1.98 ERA. The two homers allowed didn't seem that problematic even though they equaled two-thirds of the total he allowed in 2011. But the homers just kept coming. Making matters worse, Rzepczynski's strikeout rate began to fall. In the 13 1/3 innings Scrabble threw between May 16 and this writing (on Saturday, June 30), Rzepczynski has given up four homers and 25 hits with an astronomical 10.13 ERA. Unquestionably, his BABIP swinging from .154 in his first 13 2/3 IP to .457 over his next 13 1/3 (despite a below-average 18% LD rate over that second arbitrary time period) has had an effect, but the glaring stats are homers allowed and strikeouts induced.

*Rzepczynski's 2012 statistics are through play on Friday, June 29, 2012.

Rzepczynski is allowing fewer fly balls, about the same number of grounders, and about the same number of line drives that he did last season when he was so effective for the Cardinals. And yet somehow over one-third of opponents' fly balls are carrying out of the ballpark. It's a staggering total that is completely unsustainable. Regression to something closer to the league average has to happen. Nonetheless, it made me wonder if there was a reason other than luck for Rzepczynski's struggles. After all, his strikeout rate has fallen precipitously as well.

In the Post-Dispatch's "Round Two" virtual water cooler discussion, the question of whether the Cardinals were missing Dave Duncan was posed. Derrick Goold offered a theory regarding Rzepczynski's ineffectiveness under Matheny and Lilliquist as compared to Tony La Russa and Duncan:

There are times also this season when you would probably see double-barreled action in the bullpen under Duncan/La Russa and haven’t with Lilliquist/Matheny. The use of Marc Rzepczynski offers another example as Duncan pushed him into a more traditional lefty specialist role with the occasional look at righties. Rzepczynski’s role has expanded a bit with this current bullpen setup and his effectiveness has been off.

This caused me to look at Rzepczynski's platoon usage in 2011 and 2012 with the Cardinals. In 2011 under La Russa and Duncan, Rzepczynski faced right-handed hitters in 58 plate appearances and left-handed hitters in 40; 59.18% of the batters Rzepczynski faced in 2011 were right-handed. In 2012 under Matheny and Lilliquist, the lefty has tallied 65 PAs against left-handed hitters to 53 against right-handed batsmen; 55.08% of opposing hitters faced by Rzepczynski in 2012 have been left-handed. If anything, Matheny and Lilliquist are using Rzepczynski in a more traditional lefty specialist role than did La Russa and Duncan.

It would seem that Matheny and Lilliquist are putting the southpaw in positions that make it easier for him to succeed by matching him up against left-handed batters a majority of the time. Rzepczynski has had success against left-handed hitters in his career while right-handed batters have performed well against him. Here are Rzepczynski's overall numbers for 2011 from both Toronto and St. Louis and his numbers in 2012 by handed of the opposing hitter.

*The 2012 numbers are through June 29, 2012.

Hitters are performing better across-the-board against Rzepczynski this season. Left-handed hitters are hitting better against him this season than right-handers were last season while right-handers are experiencing Joey Votto-esque results against the southpaw in 2012. Here is a look at the results of PAs against left-handed batters and right-handed batters against Rzepczynski for last year to this year.

*The 2012 statistics are through June 29, 2012.

That Rzepczynki's BABIP has gone from .239 vs. left-handed batsmen in 2011 to .333 in 2012 despite a batted-ball profile that is largely similar for the platoon is somewhat heartening as it suggests the marked increase in productive results against him by the opposition is a function of bad luck. On the flip side, Rzepczynski has been rather lucky against right-handers. His BABIP against righties has fallen from .326 in 2011 to .300 in 2012 despite a 7.1 percentage point increase in their rate of line drives hit.

The decrease in strikeout percentage is about equal between left-handers and right-handers, falling by approximately ten percentage points for each side of the platoon split. This made me wonder if Rzepczynski has altered his pitch selection in a way that has driven down his strikeout rate. Specifically, whether he was throwing more sinkers in an attempt to induce more grounders.

First a comparison of Rzepczynski's pitch selection and results against left-handers in 2011 and 2012.

2011 vs. Left-Handed Batters

2012 vs. Left-Handed Batters

*The 2012 statistics are through June 29, 2012.

Rzepczynski threw his slider more often against left-handed batters in 2011. In 2012, the southpaw is utilizing his sinker more often in place of his slider. Interestingly, in 2011, Rzepczynski's slider was more effective, with a higher whiff rate and lower in-play rate. The same can be said for his sinker. Simply put, left-handed batters are swinging and missing much less often at Rzepczynski's sinker and slider in 2012.

Now here is a comparison of Scrabble's pitch selection and results against right-handed batters over the past two seasons.

2011 vs. Right-Handed Batters

2012 vs. Right-Handed Batters

*The 2012 statistics are through June 29, 2012.

The difference in approach and results against right-handers is less pronounced. Rzepczynski is using a largely similar mix of pitches this year. He has seen a slight dip in the whiff rate with his slider and a small uptick with his changeup. The biggest difference is the rate at which right-handers are putting the ball in play against Scrabble's sinker, which is eight percentage points higher in 2012 than in 2011.

The reason for Rzepczynski inducing fewer swings-and-misses and giving up more balls in play may be a lack of movement. With data from Brooks Baseball, the charts below compare his sinker in 2011 and 2012 as well as his slider in 2011 and 2012. They demonstrate that Rzepczynski is not getting as much vertical movement on either pitch this season. Whether or not this lesser movement is enough to account for the higher rate of contact is an open question.

Such a DIPS-inspired serenity has its appeal, but it is slightly off the mark. Rzepczynski has spent time as a reliever and a starter. His xFIP as a reliever is 3.28 compared to 3.94 as a starter. As a reliever, Rzepczynski is pitching worse in 2012 than he has throughout his career. And he is most certainly pitching worse by xFIP in 2012 than in 2011, when he posted a 3.18 xFIP between Toronto and St. Louis.

We have every reason to expect Rzepczynski's home rate to fall back to earth, which will make him a much more serviceable pitcher. However, there is some reason for concern regarding the declining whiff rate on his sinker and slider against both left- and right-handed opponents. We likely won't see the dominant lefty from 2011 but that doesn't mean we won't see a good relief pitcher yet this season.