Will Smith does not have the most saves of any closer in baseball. He hasn’t pitched the most innings of any closer, either. Nor does he have the best closer ERA. He doesn’t even have the best fastball. He just has the best results.
Statcast has this thing called xwOBA, which is Expected Weighted On Base Average. It adds exit velocity, launch angle, and sprint speed in concert with the traditional wOBA (Weighted On Base Average) formula. We’ve gone over both xwOBA and wOBA before, but since these aren’t something that come up in every day conversation and it’s important to know what they mean to understand why Will Smith is the best closer in baseball, here’s that wOBA definition one more time:
wOBA is a version of on-base percentage that accounts for how a player reached base -- instead of simply considering whether a player reached base.