March 23, 2006
2006--Setting the Stage
Personal CatchersTim Wakefield's knuckleball? That's one question Red Sox fans have been wondering since Doug Mirabelli was traded to San Diego. Mirabelli caught Wakefield almost exclusively--his "personal catcher." Josh Bard appears to be in position to inherit Mirabelli's role, continuing the tradition of a personal catcher for the knuckleballing Wakefield.
Though there are examples prior to the 1990's--Tim McCarver catching Steve Carlton almost exclusively, for example--the phenomenon of the personal catcher has become more prevalent in the the past 15 years. Greg Maddux' preference of Eddie Perez (also Paul Bako or Henry Blanco in later seasons) over regular catcher Javy Lopez is well documented. John Flaherty was Randy Johnson's personal catcher in 2005. The unique demands of catching the knuckleball has meant that Mirabelli has worked with Tim Wakefield for the past several seasons, giving Jason Varitek the night off.
Giving the primary catcher periodic rest is one of supposed benefits of this arrangement. With the personal catcher playing every 5th day when his pitcher's turn in the rotation came up, it created a pattern of 25-30 games per year the regular catcher would have off. This rest, in theory, would help the regular catcher from getting worn down over the course of a long season, remaining fresh enough even in September to contribute offensively. It is this question that interests me today--do personal catchers provide a measurable boost to their primary counterparts by allowing them periodic rest? Does the fact that Tim Wakefield has Josh Bard (and previously, Doug Mirabelli) as a personal catcher help Jason Varitek stay productive in September?
We can use the BP database to help answer the question. First, we need to determine who has been a personal catcher. While it's possible to research individual seasons and statements by managers about assigning a certain catcher to a pitcher, we can also look at the actual usage patterns to identify these situations, as well as any "de facto" personal catcher arrangements that may not have been made explicit. For our study, we'll define a personal catcher as one who caught one pitcher at least 20 times, while starting no more than 50 games total. This captures the fact that (a) a personal catcher works primarily with one pitcher, and (b) the personal catcher is not a fulltime player, nor even in a balanced jobshare or platoon.
By this standard, I identified 42 instances of personal catchers since 1960:
YEAR TEA CNAME PNAME GS TOT_C_GS TOT_P_GS ---- --- -------------------- -------------------- ---- -------- -------- 2005 BOS Doug Mirabelli Tim Wakefield 29 33 33 2005 CHN Henry Blanco Mark Prior 23 48 27 2005 NYA John Flaherty Randy Johnson 21 39 34 2005 PHI Todd Pratt Jon Lieber 21 49 35 2004 BOS Doug Mirabelli Tim Wakefield 30 41 30 2004 CHN Paul Bako Greg Maddux 32 43 33 2004 HOU Raul Chavez Roy Oswalt 33 48 35 2004 SDN Miguel Ojeda Ismael Valdez 20 37 20 2003 ATL Henry Blanco Greg Maddux 33 42 36 2003 BOS Doug Mirabelli Tim Wakefield 32 43 33 2003 HOU Gregg Zaun Jeriome Robertson 24 26 31 2003 TEX Todd Greene John Thomson 20 49 35 2002 ARI Rod Barajas Miguel Batista 27 41 29 2002 SFN Yorvit Torrealba Ryan Jensen 22 40 30 2001 ATL Paul Bako Greg Maddux 34 45 34 2001 HOU Tony Eusebio Shane Reynolds 24 40 28 1999 TBA Mike Difelice Wilson Alvarez 20 50 28 1998 ATL Eddie Perez Greg Maddux 32 39 34 1998 HOU Tony Eusebio Shane Reynolds 29 45 35 1997 HOU Tony Eusebio Darryl Kile 27 42 34 1996 MON Lenny Webster Jeff Fassero 30 50 34 1996 NYA Jim Leyritz Andy Pettitte 27 50 34 1994 ATL Charlie O'Brien John Smoltz 21 42 21 1994 HOU Tony Eusebio Greg Swindell 20 41 24 1992 CAL Ron Tingley Bert Blyleven 22 46 24 1992 MIN Lenny Webster Scott Erickson 24 32 32 1991 CHA Ron Karkovice Charlie Hough 20 49 29 1991 MIN Junior Ortiz Scott Erickson 28 41 32 1991 MON Ron Hassey Dennis Martinez 21 34 31 1988 MIN Brian Harper Allan Anderson 24 41 30 1987 TEX Geno Petralli Charlie Hough 21 49 40 1983 CIN Alex Trevino Mario Soto 33 50 34 1979 BAL Dave Skaggs Dennis Martinez 35 46 39 1979 PHI Tim McCarver Steve Carlton 27 31 35 1978 PHI Tim McCarver Steve Carlton 34 34 34 1977 PHI Tim McCarver Steve Carlton 36 39 36 1976 PHI Tim McCarver Steve Carlton 31 37 35 1974 ATL Paul Casanova Carl Morton 21 29 38 1972 MIN Phil Roof Bert Blyleven 20 48 38 1970 ATL Bob Didier Phil Niekro 20 48 32 1970 BOS Tom Satriano Sonny Siebert 26 47 33 1966 CLE Del Crandall Sam McDowell 24 39 28For each of these personal catchers, I took the catcher on the team with the most games started and made that the group of "primary catchers" (the personal catcher thus being "secondary" catchers). I then took every catcher who started 100 or more games in a season and was not on a team with a personal catcher as the group "fulltime catchers." The goal was to determine whether primary catchers (who benefit from periodic games off) fared better late in the season than did fulltime catchers.
I took the aggregate performance of all primary catchers through the end of August, and compared it to the aggregate performance of the group in September/October (regular season games only). I then repeated the process for fulltime catchers.
Through August After Sept. 1st Difference Category AVG/ OBP/ SLG AVG/ OBP/ SLG AVG / OBP / SLG Primary Catchers .267/.329/.376 .257/.321/.351 .01019/.00797/.02546 Fulltime Catchers .265/.332/.410 .263/.329/.396 .00225/.00246/.01383As might be expected, both groups lost some amount of productivity in September, resulting from a combination of the fatigue of a long season and the cooler weather arriving, which depresses run scoring slightly. And one group did indeed lose significantly more production than the other. Surprisingly, it was the primary catchers, who have the benefit of regular rest from the secondary personal catcher, who lost more offense. Fulltime catchers only dropped about 2 points of AVG and OBP, and 14 points of SLG, while primary catchers lost 10 points of AVG, 8 points of OBP, and a whopping 25 points of SLG. Overall, fulltime catchers lost about 16 points of OPS in September, while primary catchers lost double that amount (33 points).
So does the data above prove that personal catchers are actually a hinderance to the primary catcher? Does getting every 5th game off during the year actually cause a September slump? Not really. Note, for instance, that fulltime catchers as a group outhit primary catchers both time periods, particularly in the power category of SLG. It may be that stronger catchers hit for more power, and stronger catchers hold up better over a long season. Personal catchers didn't cause the decline in late-season offense for their primary catchers; it is mere coincidence that primary catchers as a whole weren't as good at hitting to begin with. Perhaps managers are more inclined to grant a veteran pitcher a personal catcher (and most of the pitchers on the list were veterans) when the primary catcher is known to be fragile, aging, or prone to tiring late in the season to begin with. The rest enabled by a personal catcher could be forestalling an even greater decline than has been observed. Perhaps periodic rest is not what's important, but rest when the catcher is actually feeling fatigued. Thus, a manager who gives the backup 30 starts based on the regular catcher's status regardless of who might be pitching that day is more beneficial than a personal catcher arrangement. Any of these are plausible reasons for what we observed. However, what we can say is that there isn't an immediately obvious benefit to a team's regular catcher by having his off days come on a regular basis due to a pitcher having a personal catcher on staff.
Of course, resting the other catcher isn't usually the main reason a personal catcher arrangement is instituted. It's typically driven by the pitcher's request, based on who he's more comfortable working with, or by a pitcher's unique requirements such as Wakefield's knuckleball. But the expected side benefit of scheduled rest for the regular catcher doesn't appear to have significant value over ad hoc decisions to give him the day off. So even if Tim Wakefield doesn't end up throwing exclusively to Josh Bard, there's no reason to think that the changed situation will affect Jason Varitek's bat down the stretch.