Earlier today, I took a look at the number of rookies per team throughout baseball history to see if it had anything to do with that team's record. I found that the percentage of rookies on a team correlated poorly to team success (.335 correlation coefficient). However, I said that a more thorough investigation based on team experience was in order. So here goes…

The first hurdle was to determine what team experience meant. I mean, a team may have a wily old veteran on the bench mentoring a rookie at the same position in the starting lineup. If you average the two, you would end up somewhere in between, even though the veteran may only play a third as much as the rook.

My solution was to weight each player's experience by the number of games played and then normalize by the total number of team games. The idea is to represent the experience for the team on the field on a given day. I know that this treats a pinch-hitter like a starter who plays a full game and that it under-represents modern starting pitchers, but I'm OK with that. I know Baseball Reference weights by games and at-bats, but then you separate pitchers and position players. Also, it under-represents Barry Bonds (because of the walks). I like the idea of the "team on the field" as the basis

Anyway, I ran the numbers for experience as well as player age (weighted in a similar fashion). Here are the most experienced teams in baseball history:

Hmm, I thought that we were told that players today are rushed to the majors. It seems like there are a bunch of old dolts in the majors today. Let's check age next:

The problem is that neither correlates well to winning (0.3490 for team experience and 0.2157 for age). The next thing that occurred to me is to look at age minus experience, that is the debut age (in theory) of the players. One would expect that the younger a player debuts the better he is:

Well, that's an odd mix. There are a lot of teams from World War II. Anyway, the correlation coefficient is not much better than for age (-0.2179) though teams with players who debut younger do do slightly better.

Finally the completist in me wants to show you the other end of the spectrum for each category. Here are the least experienced teams (ignoring the 1871 NA teams, the first major-league teams):

The youngest teams:

Now the youngest debut teams: