I use the adjective incredible here for its textbook definition; "too extraordinary and improbable to be believed". I literally did not believe this when I first looked at it, but it is true. Baseball is over a month into the season and most teams have played in the neighborhood of 25 to 30 games. That's not enough to cure all small samples, but you'd expect that most team-level stats have stabilized by now. Even if not, the following is still amazing to me.
You may recall that when we played the Blue Jays I pointed out, and the series preview listed, them as having a very good defense. That's still true, even though they made some goofy errors when playing the Mariners. When only looking at how often defenses turn batted balls into outs, the Blue Jays are currently the best in the Majors.
Toronto Blue Jays' defense: .245 BABIP, .261 RBBIP*
They've built up that value almost entirely on ground balls where the league has a BABIP of .230 and the Blue Jays have surrendered only a .146 BABIP. In terms of runs saved, that's almost 24 runs worth of prevention already, in just 27 games played. That's pretty nuts, but isn't the part that left me incredulous. What did was what appears on the other end from Toronto, namely the distance it takes to reach the team with the league's worst RBBIP*.
Milwaukee Brewers' defense: .345 BABIP, .361 RBBIP*
A full 100 points worse in both measurements! It's only one-sixth of the way into the season but that's an enormous difference. It's amazing that the Brewers have managed a 12-14 record with defense that leaky that doesn't make up for it at the plate.
*RBBIP = Reached base on ball in play. It's BABIP but includes errors.
The Mariners, by the way, currently have baseball's third-lowest RBBIP at .282, mostly from fly ball defense. All numbers are park-adjusted.