Mains: Change agents: measuring team turnover

From SABR member Rob Mains at Baseball Prospectus on January 7, 2019:

In March 2017, I examined the teams that looked to be undergoing the most change to their lineups in both the National League and the American League. I based this on each team’s 2016 plate appearances (for hitters) and innings (for pitchers), and compared them to our PECOTA projections for the 2017 season. At the time, we projected the Mariners to have the greatest turnover in baseball. When your general manager is Jerry Dipoto, that’s not a surprise.

Way back on March 17, 2017, reader Collins commented:

It would be interesting to see how much turnover there has been from year to year, for each team.

Collins, it’s taken me almost two years, but I’ve finally gotten around to it!

This is going to be a multi-part series. Since the formation of the American League in 1901, the two leagues have played 118 seasons contested by 2,466 teams. I could list the three teams that changed the most and the three that changed the least all time, but I think that would give everybody short shrift. There have been major changes in baseball—World Wars, expansion, the influx of non-white and foreign-born players, free agency—that have affected player movement and roster construction. I’m going to look at turnover a decade at a time.

Read the full article here:

Originally published: January 7, 2019. Last Updated: January 7, 2019.