It's the best pitch in baseball, according to no less an authority than David Price. It's a breaking pitch that's thrown harder -- 88.3 mph on average, per Statcast™ -- than 68 other starting pitchers throw their fastball, at least among those who have done so at least 40 times. It causes batters to contact nothing but air 43.4 percent of the time they swing at it, the seventh-highest rate on the pitch in baseball.
It's Chris Archer's slider, and it's the primary reason why he's gone from "pretty good young pitcher" to "unhittable ace" in 2015.
If that sounds like high praise, well, it is, but it's also earned. Over his past three starts, Archer struck out 38 hitters without walking any, making him the first pitcher in at least a century to put together three straight starts with no walks and at least 10 strikeouts. Unsurprisingly, he was named the American League Player of the Week for the first week of June. So far in 2015, his 1.84 ERA is tied for third best, and his 2.09 FIP is well ahead of those of Max Scherzer and Corey Kluber for the best in the game. We're not overselling him. He's really been that good.
So, about that incredible slider: Archer has always had one, but not quite like this. In 2006, just before Cleveland selected him in the fifth round of the Draft, Baseball America's Draft preview suggested that "Archer's best pitch is a sharp slider that he throws in the 78-81 mph range." In 2012, he told MiLB.com that it was his "second-best pitch," and that it was thrown in the 84-86 mph range.
At the time, Archer may have preferred his four-seam fastball, but the slider was still his most effective pitch when he reached the bigs later that season. Compare his wOBA against -- that's Weighted On Base Average, which is roughly on the same scale as batting average -- in his first three seasons among his three primary pitches:
Archer's fastballs have been inconsistent, but it's always been the slider that's his best. Of course, if he always had an effective slider, why is he only taking the next step toward stardom now? Because he's throwing it more -- nearly 39 percent of the time this year after throwing it 28.8 percent last year. And he's throwing it harder. Remember when the scouting reports said low-to-mid 80s? It's gone up, consistently, a mph per year each of the past three seasons.
Even just on a monthly basis within 2015 alone, he's throwing it harder, from 87.09 mph in April to 87.64 mph in May to 89.62 mph in June, which is to say that he's throwing a pitch that does what it does at nearly 90 mph.
One such slider, to Seattle's Austin Jackson last week, was actually tracked at 94.5 mph, which is just not right. But he's not just throwing it harder and more frequently. It's also unique, moving nearly 2.5 inches different than it did when he arrived in 2012. Hitters this season have a .202 wOBA against his slider, and have just six extra-base hits against it while striking out 75 times.
Interestingly enough, despite the higher-than-usual velocity, this is all out-of-the-hand speed. That is, Archer is not gaining perceived velocity by releasing the ball closer to the plate, like many pitchers do. His 5.48-foot slider extension, per Statcast™, is the lowest of any of his pitches -- his rarely-used changeup comes out at 6.2 feet -- and so his perceived velocity to the hitter is 1.23 mph slower than the actual release speed. Of 84 pitchers to throw a slider 100 times, only 18 lose more perceived velocity, which should tell you something about how hard he's letting it go.
It's worth noting that new Rays manager Kevin Cash spent the previous two seasons as Cleveland's bullpen coach, where he helped Kluber and Carlos Carrasco develop deadly sliders of their own. Despite injuries to Alex Cobb, Matt Moore, Jake Odorizzi, Jake McGee, Drew Smyly and others, Tampa Bay actually has the best ERA in the AL. That's due to considerable pitching talent on hand, and perhaps Cash's influence. But a big part of it is also about a good young pitcher emphasizing his best pitch to take the step forward to be a great young pitcher. It's about Archer, quietly one of baseball's best.
Mike Petriello (@mike_petriello) is an analyst for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.