Mariano Rivera (NYA) reached a milestone Wednesday afternoon as he pitched in his 1000th game, 990 of them in relief. At seasonal age 41, the Yankees closer continues to impress. With a 1.71 ERA he's going for his fourth straight season with an ERA under 2.00. If he succeeds, it would he his eleventh such season in his career.
The current streak of sub-two ERAs coincides with the PITCHf/x era. The following graph sums up Rivera's dominance in that time quite well:
The first thing to notice is that Mariano uses one pitch, a cut fastball thrown between 90 and 94 miles per hour. There's nothing soft, no off speed pitch to fool the batters. The cutter does it well all by itself.
Rivera induces swings. Batters swung at 49.4 percent of his pitches, which puts him in the 94th percentile among all pitchers in the majors in that time. Look at what they are swinging at, however. Batters swing at 38% of the pitches that should be called balls. That is the 100th percentile, the best in the majors. Rivera gets batters to see balls as strikes, and swing at them. In general, batters tend to get worse results when they swing at balls.
That's not the only effect of the cutter, however. Of the pitches batters take, 36.1% of them are strikes. That may not seem like much, but the major league average is 31.8%, and Rivera's number ranks in the 95th percentile. Not only is Mariano great at getting batters to swing at balls, he's almost as good at getting them to take strikes.
And he does it all with one pitch.