After categorizing starting pitchers by strikeout and groundball rates yesterday, today's article is focused on relievers. Previous entries with supporting information as to the whys and wherefores of this study can be accessed at the following links: 2008 SP, 2007 SP, 2007 RP, 2006 SP and 2006 RP.

The universe includes strikeout and groundball data for every reliever in the majors (defined for this exercise as those with 30 or more innings who started less than one-third of the time). There were 231 pitchers who met these requirements in 2008. Among these qualifiers, the average K/BF rate was 19.68% and the average GB rate was 43.74%. By comparison, starters had a mean K/BF rates of 16.90% and GB% of 43.45%, respectively. While the groundball rates were virtually the same, the average strikeout rate among relievers was 2.78 percentage points higher or 16.4%.

The mean K and GB rates are highlighted in red in the graph below. These averages separate the starting pitchers into four quadrants. By placing pitchers in quadrants, one can easily distinguish those with above-average strikeout and groundball rates (referred herein as the northeast quadrant), above-average strikeout and below-average groundball rates (southeast quadrant), above-average groundball and below-average strikeout rates (northwest quadrant), and below-average groundball and strikeout rates (southwest quadrant).

The simple average and weighted average (by innings) ERA and RA are detailed in the table below.

The message is the same for relievers as it was in yesterday's table for starters:

• Pitchers with above-average K rates outperform those with below-average K rates.
• Pitchers with above-average GB rates outperform those with below-average GB rates.
• Pitchers who combine above-average K and GB rates outperform all others.

As with the starters, it is always fun to look at the outliers. Starting at the upper end of the graph, Roy Corcoran had the highest percentage of groundballs among all pitchers (starters or relievers). Moving clockwise, the other outliers consist of Scott Downs, Ramon Troncoso, Rafael Perez, Mariano Rivera, Takashi Saito, Brad Lidge, Jonathan Broxton, Octavio Dotel, Carlos Marmol, Grant Balfour, Juan Cruz, Alex Hinshaw, Troy Percival, Eddie Guardado, Brad Hennessey, Todd Jones, Horacio Ramirez, and Chad Bradford. Saito, Broxton, and Bradford also stood out in their respective quadrants the previous year.

Data and graph courtesy of David Appelman, FanGraphs.

Let's drill down and take a closer look at each of the quadrants. The NE, SE, and SW quadrants are listed by K/BF, while the pitchers in the NW quadrant are in order of GB%.

Lidge not only tops this elite group of relievers but is one of only two pitchers to exceed a 30% strikeout rate for three consecutive seasons. He was 48-for-48 in save situations (including the postseason) and led all relievers in Win Probability Added. For my money, Lidge was the best relief pitcher in baseball last year.

Saito is the other reliever who has whiffed at least 30% of the batters faced during the past three campaigns. He suffered a sprained ligament in his elbow last summer and was not tendered a contract by the Dodgers. The 39-year-old righthander signed a one-year deal with the Red Sox with a team option for 2010. Along with the newly acquired Ramon Ramirez and holdovers Jonathan Papelbon and Manny Delcarmen, Boston will have four members of the NE quadrant in its bullpen in 2009, tied for the most in baseball. Despite losing Saito, the Dodgers will also head to camp with four relievers from the NE quadrant: Broxton, Hong-Chih Kuo, Troncoso, and Guillermo Mota, who was signed in January.

Rivera and Perez qualified for the 25-50 club for the second straight year. Matt Thornton and Joba Chamberlain, who split his season between the starting rotation and the bullpen, are also card-carrying members of the 25-50 organization. Joba will either hook up with Mo to form a "lights out" eighth and ninth inning tandem or join fellow NE quadrant starters A.J. Burnett and CC Sabathia in the rotation. It's a nice "problem" for Yankees manager Joe Girardi to figure out this spring.

Balfour had the highest strikeout rate of any big league pitcher last year. Although the 31-year-old righthander got knocked around in October, he put up remarkable stats during the regular season (summarized by a 1.54 ERA and 0.89 WHIP). It will be interesting to see how the well-traveled and hard-throwing Balfour performs in 2009.

Cruz and Marmol are no strangers to the upper end of the southeast quadrant, placing third and second, respectively, in 2007. The strikeout artists swapped places in 2008. Cruz became a free agent after the season and remains unsigned days before pitchers and catchers report to spring training, primarily due to the fact that the acquiring team will be forced to part with a first-round draft pick as compensation for a Type A player. Marmol, who has struck out 210 batters while allowing only 81 hits in 156.2 IP over the past two seasons, is the favorite to succeed the departed Kerry Wood as the Cubs closer in 2009.

The NWQ is comprised of 11 relievers with groundball rates in excess of 60%, including Cla Meredith and Brandon League, both of whom have eclipsed the 70% mark in one of the past two seasons.

As measured by WPA, Downs (14th), Brad Ziegler (9th), and Bobby Jenks (5th) were the most successful relievers in this group. Ziegler posted a 3-0 record with a 1.06 ERA while saving 11 out of 13 opportunities for the Oakland A's even though he wasn't called up to the bigs until the last day of May. Jenks fell out of the NEQ for the first time as his K/BF has dropped from 29.76% in 2005 to 26.67% in 2006 to 22.49% in 2007 to 15.64% in 2008. The trend is not his friend.

I don't think there is a single reliever in the bottom half of this quadrant that I would sign with your money, much less mine. At the bottom of the heap is Todd Jones, who lost his role as closer to Fernando Rodney, a member of the SEQ, in July and thankfully announced his retirement in September. To his credit, Jones is 14th on the all-time list for career saves. I don't know if that says more about him or the validity of the save statistic.