The relief pitcher who has had the most dominant start to the season so far throws 103 miles per hour, and there's a good chance you've never even heard of him.

Until now.

Meet Ryan Helsley, the 27-year-old Cardinals right-hander who not only has thrown MLB's fastest pitch this season -- 103.1 mph! -- but also sports these stats (entering Thursday's games): eight appearances, 10 innings pitched, one single solitary hit allowed, zero walks and 20 strikeouts.

That's one baserunner allowed and a remarkable 64.5 percent strikeout rate, the best in MLB by a wide margin. It translates to a microscopic 0.17 expected ERA, which is easily the lowest among all pitchers who have had at least 10 balls put in play against them. His FIP? Try negative-0.90, which almost seems impossible.

Granted, it's only 10 innings, so the sample size still is small, but it's also enough to show that the hard-throwing Helsley has supreme stuff. Quite simply, no pitcher has opened a year like this -- racking up this many strikeouts while limiting hits and walks to this extent -- in AL/NL history.

Among pitchers to start a season with one or fewer hit allowed and no free passes across their first eight outings, Helsley's 20 strikeouts are the most on record. Here's what that list looks like:

• Ryan Helsley, 2022 Cardinals: 10 IP, 1 H, 0 R, 0 BB, 20 Ks
• Kenley Jansen, 2015 Dodgers: 8 IP, 1 H, 0 R, 0 BB, 14 Ks
• Seranthony Dominguez, 2018 Phillies: 9 IP, 1 H, 0 R, 0 BB, 9 Ks
• Ryan Dull, 2016 A's: 8 1/3 IP, 1 H, 1 R, 0 BB, 9 Ks
• Mike Remlinger, 2002 Braves: 6 1/3 IP, 0 H, 0 R, 0 BB, 9 Ks

So how is Helsley -- a fifth-round Draft pick in 2015 who debuted in '19 and is coming off a '21 in which he posted a 4.56 ERA, a 1.42 WHIP and fewer strikeouts (47) than innings pitched (47 1/3) -- doing this?

Health

Let's start here. Health is one key factor, as Helsley battled a balky left knee for most of 2020 and '21 that caused him to alter his mechanics and led to a stress reaction in his right elbow that cut short his season last August.

As MLB.com's Cardinals reporter John Denton wrote recently: "Helsley said his pitching improvement -- and the increased velocity on his fastball -- can be traced to the health of his left knee after he underwent arthroscopic surgery during the offseason. Helsley said he originally injured his knee prior to Spring Training in 2020 and pitched in pain much of the past two seasons before shutting things down near the end of last season."

“It just feels good to be healthy," Helsley said, "to be able to trust my stuff and trust that my body is going to be strong again."

That has provided Helsley with the opportunity to showcase his repertoire, namely good old No. 1, a pitch that's been a plus for him dating to when he peaked as St. Louis' No. 8 prospect in 2018.

Heater

Helsley has harnessed a heck of an unhittable heater to this point. The 6-foot-2, 230-pounder has thrown his four-seamer 72 times and has yet to allow a knock, as batters are 0-for-16 with 11 strikeouts against the pitch.

His fastball's average velo of 99.2 mph -- up about two miles per hour from 2020-21 -- ranks sixth in MLB, and his ability to reach back for even more when he needs it is even more impressive. Consider this:

Most Pitches Thrown 102+ MPH in 2022
6: Jhoan Duran, Twins
3: Ryan Helsley, Cardinals
2: Andrés Muñoz, Mariners
1: Hunter Greene, Reds
1: Jordan Hicks, Cardinals

All of that puts Helsley in the 100th percentile -- as in, among the absolute best -- in fastball velo. But that's only part of what makes his four-seamer so effective.

High Spin and High "Rise"

It also possesses an average fastball spin rate of 2,569 rpms -- good for the 98th percentile.

That tremendous spin is what gives Helsley's heater the effect of rising significantly more than the average four-seamer. He generates 21 percent more rise compared to average on the pitch, ranking just outside the top 10.

That's elite vertical movement, and it's coming on a pitch that regularly tickles triple digits.

Put another way: On average, the 9.2 inches of vertical movement Helsley gets on his four-seamer means that it drops the second least of all four-seamers in MLB. In other words, when Helsley throws high heat, it stays high, as FanGraphs' Ben Clemens pointed out recently in highlighting Helsley's early season success. And he's been doing that more often this season.

Here's a look at his four-seam location heat map from 2021:

And this is from 2022:

The dark red -- which indicates the highest volume of pitches -- has bumped up in the zone noticeably, and that is where pitchers have been getting whiffs more and more in recent seasons. A quick check of Helsley's whiff rate on his four-seamer proves as much: After a 15.7 percent mark last year, it has spiked to 42.5 percent, which is in the top five in baseball (minimum 25 four-seamers swung at).

Hard-Hit ... Not

One other way Helsley has excelled early? Limiting hard contact.

His average exit velo allowed is a meager 81.5 mph, which checks in as the third lowest among pitchers with at least 10 batted balls against. He's also yet to allow a single barrel, and only 2.6 percent of swings against Helsley have resulted in even a hard-hit ball (95+ mph).

Before getting too carried away with Helsley's performance, however, it's worth pointing out again that all of this is based on a small sample size of just 10 innings to date. Not only that, but there's the fact that Helsley is something of a victim of his own success in that there are so few batted balls -- just 11! -- to evaluate because he has recorded such a high percentage of his outs via strikeout.

One last word of caution, too: Control has been an issue for Helsley in the past, as he entered the year with only 96 career innings in the Majors and a rate of 4.4 walks per nine. Can he maintain anything close to the near-impeccable command he's shown?

Of the 31 batters Helsley has faced so far, only six have reached a three-ball count -- and of those, he's been able to strike out five. That's a good sign, if yet another tiny sample.

If this ability to avoid walks and too many hitters' counts is for real? A healthy Helsley armed with his elite high heat looks poised to break out. You heard it here first.