How Will Joe Mauer Age?

With the eye towards the future, the Twins will need to decide who is going to be a part of it. The decision doesn't apply to Joe Mauer, as his contract is prohibitively expensive and combined with his hometown popularity, he's in Minneapolis for the long haul.

That begs the question of what we should expect from Mauer over the next 6.5 years. An awful lot of the answer to that depends on his health. But, as far as catchers go, Mauer is a pretty safe bet to play 130-140 games a season and behind the plate for a majority of those. Since his first full season he's played an average of 123 games per year, despite missing half of the season in 2011. Interestingly (and predictably) his percentage of games behind the plate has been in decline:

*2012 is trough 111 games.

So going forward I think it's fair to suppose he'll play 140 games, about 70 of them behind the plate. As he's demonstrated this year, the extra time will allow him to stay healthy and in the lineup.

Now, for the matter of how his bat will hold up. His profile as a line drive hitter generally ages more gracefully than those who depend on speed or power. Between the bat and his tremendous plate discipline, I would say he should be an above average hitter at any position for the duration of his contract. But I'm a homer and am able to convince myself of just about anything. So I'll present some tools that can be used to project Mauer's remaining career.

The first tool is a similarity score. Baseball-Reference.com compares players to find the 10 other players  from history most similar to any given guy. Here's the top ten list through age 28 (going into this season):

1. Mickey Cochrane (HOF)
2. Bill Dickey (HOF)
3. Jason Kendall
4. Yogi Berra (HOF)
5. Victor Martinez
6. Jose Vidro
7. Cary Carter (HOF)
8. Derek Jeter
9. Charlie Gehringer (HOF)
10. Nomar Garciaparra

Cochrane played 5 seasons after his age-29 season, and he was consistently a very good hitter. His OPS+ was 135 during that span, compared to a 126 OPS+ in his first 8 seasons. Bill Dickey, Gehringer , Berra and Jeter were similarly successful deep into their careers.

#3 on the list, Jason Kendall, is a favorite comparison of baseball writers. He shares a similar profile, good hitter with patience and below average power as well similar eras. Up through his age-29 season, Kendall hit .304/.385/.422. Comparable to Mauer's .323/.404/.468 (although, when one factors in the offensive environments it's not so close). But then Kendall dropped off considerably, .270/.344/.329. Some have forecasted this as a possibility for Mauer, I'm not sure that I buy it.

The others on the list don't compare very well for a number of reasons. Martinez would be good, in that he's moved out from behind the plate, but his career has yet to unfold. Vidro is recent enough where I was able to watch his prime and I don't see any similarity at all. In the same vein, I don't agree with the understand the Nomar comp. He had some pretty severe injury issues that wrecked his career. Not that the same fate isn't possible for Mauer, but we can't predict career ending injuries.

Similarity scores yield some interesting results, with a range of possibilities. The conclusion I draw, is that he's played like an all-time great, who are usually able to maintain their skills into their late 30's. However, the list is also a reminder of the omnipresent possibility of decline (Kendall) and catastrophic injury (Garciaparra).

The other useful tool is Baseball Prospectus PECOTA system. PECOTA is a projection system that actually uses similarity scores to build its forecasts. It's often lauded as the most accurate projection system in sports, so it's not a bad glimpse into the deep future.

Baseball Prospectus "Crystal Ball" projects a steady decline for Mauer, in which he hits between .270 and .311, with some decent power. The production yields True Averages (an amalgamation of offensive worth) of .270-.306 where .260 is the league average and WARPs between 2 and 4.5.

PECOTA is generally fairly conservative, especially on the high end, so it's very possible he outplays those 'ceilings'. In fact, it's rare to see PECOTA project a hitter to have this much success that far into the future.

Both tools point to sustained production from Mauer for the duration of his $23 million a year contract. Considering inflation is essentially zero these days, Joe is going to have to be productive to be worth that kind of coin.

In conclusion, the Twins seem to be in a decent place with Mauer for the next 6 and a half years. The biggest risk will be avoiding injury, if he can do that, we'll be watching a future Hall of Famer for the next half decade.