Kenley Jansen is Mariano Rivera 2.0

Kenley Jansen has never been better.

On Sunday, Jansen threw 12 pitches — 12 cutters — and 11 for strikes to close out the Reds during a 1-2-3 ninth. Video evidence of the simplistic, ruthlessly efficient, Jansen Way:

When he struck out Eugenio Suarez to end the game, Jansen recorded his 50th strikeout of the season. He has still not walked a batter. He keeps bettering his MLB record which he set earlier this month in Milwaukee, when he recorded his 36th strikeout of the season without issuing a walk.

In an era when relievers have never missed more bats, thrown harder, or produced more devilish breaking pitches, Jansen is arguably the best reliever in the game. He leads all relievers with a 0.30 FIP, 0% walk rate (LOL), and a K-BB rate of 47.7% (LOL). He is second in relief WAR (1.9) to Craig Kimbrel (2.1) and is fifth in ERA- (22).

He has the eighth-lowest in-zone contact rate among relievers (73.2%) and the ninth highest out-of-zone swing rate (39.6%), which is a career best. You can view all the aforementioned and sortable leaderboards here.

He is a one-trick pitcher, but it is a heckuva trick. He has thrown his cutter on at least 84% of his offerings every year since 2012, but he’s leaning on it at a carer-high 91.2% rate this season. While the number of pitches in the strike zone (54.3%) is near his career average of 53.6%, his first-pitch strike rate (79.4%) has jumped 11 points from last season (68.1%) and is well above his carer mark (64.9%).

The Jansen cutter ranks second in vertical movement among all major league cutters (9.35), third in horizontal movement (3.19), third in whiffs per swing (37.26%) and first in pop-ups per balls in play (22%), according to the Baseball Prospectus leaderboards.

The pitch is getting better. It’s moving more and generating more whiffs and weak contact compared to last year and his career averages (33.4% whiffs per swing) and 14% pop-up rate.

And because of the cutter reliance, because of his utter dominance, the comps to Mariano Rivera have been common throughout his career.

But the comp is growing in relevance. Jansen is no longer like Rivera. He is Rivera, at least through eight major league seasons. He is as close to Rivera as anything we might see. While Craig Kimbrel is arguably more dominant, Jansen’s profile is a better match and perhaps a batter guide of what to expect going forward. Some, especially those residing between Connecticut and Philadelphia on the Eastern seaboard (or having migrated to Florida), would consider comparing any reliever to Rivera as sacrilegious. But though their first eight seasons, Jansen is Rivera —- minus the World Series rings and opportunities.

Consider FanGraphs’ ERA- leaderboard since 1997:

The entirety of Rivera’s career was not watched by PITCHf/x tracking, but Rivera did not reach 80% cutter usage until 2008, according to the PITCHf/x and FanGraphs pitch tagging. That was Rivera’s Age 38 season. Rivera leaned on the pitch at an 82% or greater rate throughout the rest of his career, retiring after 2013.

While Jansen and Rivera’s first eight years are remarkably similar when accounting for run-scoring environment and ballparks, Jansen, 29, is three years younger than Rivera was in his eighth season.

Jansen should, in theory, have more tread left on his tires, though having 11 more Rivera-like seasons is asking a lot. The fact that Jansen has leaned more on the cutter earlier in his career might compromise his longevity if you are among the believers that the pitch places more stress on a pitcher’s elbow and shoulders relative to other pitch types. Some organizations believe this, like the Orioles, which had Dylan Bundy shelve his cutter earlier in his career.

While linear weights is not a perfect measure to gauge pitch effectiveness, it does boil down value to one measure, and cutters don’t age any less well than most offerings:

Not only do Jansen and Rivera test conventional wisdom in regard to how many pitches a pitcher requires to be elite, even in the bullpen, perhaps they will also change some thinking about the cutter.

Jansen is a glaring reminder to remain open-minded.

Would every organization have experimented with Jansen, then a struggling catcher with the High-A Inland Empire 66ers, as a pitcher in 2009? He slashed .202/.268/.303 in 26 games as a catcher, and struck out 19 in 11 2/3 innings that season as he chose the right fork in the road.

Would every staff allow a pitcher to rely so heavily on one pitch? And it is perhaps that usage that is allowing such a mastery of the pitch. After a walk rate that hovered near double-digits earlier in his career, Jansen is well on his way to posting a sub-5% walk rate for a third straight season. Heck, maybe he will not a walk a batter this season.

Jansen is so unusual he invites the only comp that makes sense: Mariano Rivera.