We are getting to the end of the third month of the season, which means that we stop talking about players and teams off to hot or cold starts and start talking about how their year looks. This can be good or bad news for teams -- good for surprise contenders like the Milwaukee Brewers and New York Yankees, and bad for teams in big holes like the New York Mets and the San Francisco Giants. What this time of year does afford us, though, is the ability to take what a team has done so far this year on its own merit and not refer back to the previous season as much.
With that in mind, I wanted to take a broad view of the league's defensive landscape, assessing where teams stand relative to each other by defensive runs saved (DRS) and seeing where some clubs have an opportunity to improve. To give some analytical rigor to the proceedings, I took a weighted average of each team's total DRS the last two seasons. This season's total was prorated to a full season, and then the two seasons were averaged with two parts 2017 and one part 2016. This allows 2017 to count more, but doesn't fully discount what a team did last year, as most players are still on the same team and we don't want to overvalue results from this year alone. Then I ranked each team by this weighted average, and grouped the teams into tiers based on those values.