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The Cardinals first got a sign that this Ryan Helsley -- someone who is suddenly one of the most unhittable relief pitchers in all of baseball -- was a different pitcher seven games into the season April 16 in Milwaukee.

With the Cardinals clinging to a 1-0 lead and the potential tying run on base, Helsley was called upon to relieve starter Steven Matz with slugger Hunter Renfroe coming to the plate. After falling behind 3-1 in the count, the St. Louis reliever turned to his arsenal of pitches to get his team out of the jam. With the Milwaukee crowd roaring, Helsley surprised Renfroe with an 86.1 mph slider for a strike. A pitch later, Helsley quieted the crowd and ended the threat by blowing Renfroe away with a 101.2 mph fastball.

“To throw the 3-1 slider there, that took some real guts,” Cardinals manager Oliver Marmol recalled. “And then to come back 101 on the fastball, that was impressive.”

Helsley, 27, has been one of the most impressive relievers in all of baseball this season. Following another dominant outing Friday in San Francisco -- one in which he struck out four of the five batters he faced and picked up his first victory -- Helsley has started the season by striking out 20 of the first 31 batters he’s faced while allowing just one hit over 10 innings. Not only has Helsley thrown the fastest pitch in MLB this season -- a 103.1 mph fastball May 1 -- he has thrown three of the five fastest strikeout pitches of the season. In his two innings of perfect relief work against the D-backs, Helsley joined teammate Jordan Hicks, Aroldis Chapman, Henry Rodriguez and Joel Zumaya as the only MLB pitchers to record three strikeout pitches of 101-plus mph in the same game since pitch tracking began in 2008.

Against the Giants, he struck out another two hitters with 101-plus-mph pitches.

For the season, Helsley is averaging 18 K's per nine innings. In his three previous MLB seasons, he had never averaged more than 8.9 strikeouts per 9. So, what gives? As it turns out, Helsley’s decision to have surgery on his left knee following last season has made all the difference for him.

“It really started bothering me at the beginning of 2020, the COVID year, and I thought I had it settled and then it came back in the 2021 Spring Training,” Helsley said. “I was able to manage it during the season and I don’t know that I noticed it when I was out there during games, but when I’d try to work out, I’d definitely notice it.

“For me, I’d feel it when I would land or when I would bend and I was in that position where it would hurt,” he added. “Without me even noticing it, I think it caused me to change my mechanics or it caused to not be as consistent as I wanted to be because I was cognizant of the pain in the knee. It also caused me to put more stress on my arm.”

Compensating for the knee led Helsley to having a stress fracture in his right elbow late last season. With his knee and elbow now healthy, Helsley can once again attack hitters with his dazzling array of pitches. His curveball is in the high 80s, his cutter is in the high 90s and his fastball, of course, has gotten up to as high as 103.1 mph.

“When he has command of all three pitches, he can be downright nasty,” Marmol said.