Papelbon’s Fastball

Boston’s bullpen is struggling this season. Collectively, Red Sox relievers have a 4.68 xFIP, besting just the Indians, Royals and Angels among American League clubs. The only Sox reliever with a sub-four xFIP is Daniel Bard, at 3.29.

You may be surprised to learn that Jonathan Papelbon, he of 2.6 Wins Above Replacement per season as a full-time reliever from 2006-2009, is among the most egregious offenders.

In 24 innings pitched, the famed river dancer is walking a tight rope — his 3.00 ERA doesn’t look so bad, but his xFIP sits at 5.02. With -0.3 WAR, Papelbon has arguably been the least effective of Boston’s bullpen options.

Papelbon has a career-low 7.13 K/9 and a career-high 4.5 BB/9. He’s getting swinging strikes 11.1 percent, still above the 9.3 percent average for MLB relievers but below his 13.3 percent career average. The 29-year-old is also putting fewer pitches within the strike zone — 48.2 percent, compared to a career 53.6 percent average. When Papelbon does throw a pitch in the zone, batters are putting the bat on the ball more often. His in-zone contact rate is 89 percent, well north of his 81.9 percent figure as a major leaguer. If Papelbon’s batting average on balls in play were closer to his career .275 mark than his current .198, his struggles would be more apparent.

Sample size caveats apply, but 2010 continues a clear downward trend in the effectiveness of Papelbon’s fastball. During his career, Papelbon’s heater has been one of the best offerings in the game. His mid-90s gas has been worth +2.07 runs per 100 pitches. However, that fastball hasn’t been near as dominating lately:

Papelbon’s Run Value Per 100 pitches with the fastball, by year

2005: +0.69
2006: +3.24
2007: +3.29
2008: +2.21
2009: +1.49
2010: -0.34

Papelbon had the highest fastball run value/100 pitches among relievers in 2006. He placed second in 2007 and fifth in 2008. Last year, he still managed to sneak into the top 20. But this season, his fastball has been about as valuable as those of Danys Baez and Kanekoa Texeira.

Trip Somers’ texasleaguers site has three years of Pitch F/X data on Papelbon. There aren’t any large changes in terms of velocity or movement, but the strike, swing and whiff rates on Papelbon’s fastball are heading in the wrong direction:

2008: 71.3 Strike%, 56.3 Swing%, 11.5 Whiff%
2009: 67.5 Strike%, 51.8 Swing%, 10.4 Whiff%
2010: 67.0 Strike%, 49.7 Swing%, 10.0 Whiff%

It’s dangerous to infer too much from a few months of poor pitching from a reliever. But Papelbon’s performance as Boston’s closer has gone from awesome (2.78 xFIP from ’06 to ’08) to acceptable (3.98 xFIP in ’09) to replacement-level.

The odds that he continues to at this pace are very low — Papelbon has a long track record as one of the best relievers in the majors. But if the Red Sox are going to overcome New York or Tampa and snag a playoff spot, they’ll need their stopper to pick up the pace.