There has been much discussion about whether the Red Sox should try to retain Jason Varitek. Aside from having Scott Boras as his agent, the basic argument can be boiled down like this:
PRO: Varitek is an amazing catcher with a fantastic memory and is a huge boon to the pitching staff (a fact that I have never heard anybody dispute)
CON: Varitek has been a pretty poor hitter over the last 1.5 seasons (also a fact that I have never heard anybody dispute.)
I would argue that the Red Sox should keep Varitek, assuming they can find a 2-year contract that makes sense. I believe that offensive contributions from catchers are thought to be more significant than they are.
Those of us old enough to remember baseball back in the 80s and earlier recall that catchers were rarely major offensive forces. Players like Johnny Bench and Gary Carter were very much the rarity and not the norm. It's easy to forget now, but when Mike Piazza first came along, he was so often heralded as the greatest offensive catcher since Bench or perhaps ever. The graph below shows that it was during The Steroids Era that catchers saw unprecedented offensive success, at least when measuring by number of 20 HR, 75 RBI seasons.
The red points are the data and the black line is a 5-year average.
It wasn't until the mid-1990s that as many as 5 catchers ever had such output in the same year. At this time, the 5-year average hit 4 catchers per year, an average that was never reached previously in MLB history.
It's also true that we've seen a significant dropoff from 1999 to this past season. The high of 5 catchers in 1999 has come down to just 2 catchers the last 2 seasons.
However, the above graph is tough to understand in a vacuum. For instance, the number of teams and number of games in a season has changed over the years. In theory, more catchers should be getting 20 HR, 75 RBI seasons these days than in past decades simply because there are more teams now. Plus, trends in the game have changed, with run scoring going through peaks and valleys, making it more or less likely at different times for any given player to achieve certain statistical totals. We know that lots of players accumulated large HR and RBI totals in The Steroids Era.
So, let's normalize performance by catchers. First, I determined the total number of 20 HR, 75 RBI seasons each year by players at any position, and then found the fraction each year that were achieved by catchers. That tells us a lot more while eliminating factors such as number of teams or games.
Wow, I bet you weren't expecting this, were you? What this graph is telling us that pretty continuously over the last 80 or so years, catchers have contributed fewer and fewer 20 HR, 75 RBI seasons to baseball. Some of this could be because fewer catchers are playing enough games to achieve these totals, but my guess is that it's more than that. Other than the extreme drop-off in the three year period 1988-1990, catchers today are contributing the smallest percentage of 20 HR, 75 RBI seasons since the mid-1940s.
Why do I think this means that the Red Sox should resign Varitek? Basically, I'm saying that as a .220 hitter, his offensive contributions are not so much less than could reasonably be expected. An average catcher over 450 AB might produce 15 to 20 more hits a year, and while those additional hits would produce a few more runs, that difference may well be balanced by Varitek's added value to the pitching staff as compared to an average catcher.
Mind you, if Boston had the opportunity to go out and get an above-average catcher such as Brian McCann, that guy would likely be more valuable than Varitek. But with good catching at such a premium, as it usually has been for most periods in baseball history, Boston is unlikely to be able to acquire such a player and is far better off sticking with Varitek.