That is how he ended up with the Bridgeport Bluefish of the independent Atlantic League. Johnson is the team’s first baseman, but he also throws regularly in the bullpen and plans to soon take his knuckler into games. He is scheduled to throw a simulated game during the team’s next homestand.

“He’s like a Little Leaguer — raw, trying to learn how to pitch, which is great,” said the Bridgeport pitching coach, Jesse Litsch, a former Toronto Blue Jays starter. “He’s not starting from zero, because he’s seen enough. He knows how to throw. Being able to get that mind-set of going toward the catcher, staying on your backside and getting the hands out of the glove has been a process for him. But he’s been around the game enough, and he’s climbing quick.”

Johnson has fiddled with the knuckleball since childhood. His father, Ron, would throw him a pitch he called the Dancing Dazzler, entrancing Johnson and his friends, who could rarely hit it. The more Johnson toyed with his own version, the better he became at removing the knuckleball’s enemy: spin.

In 2013, when Johnson played for the Yankees’ Class AAA team, a coach, Gil Patterson, said he had heard of Johnson’s trick and asked him to test it in the bullpen. Encouraged, Johnson hoped to show off the pitch to his next team, the Toronto Blue Jays, the next spring. Then he pulled on a stray cord wrapped around a stack of weights just before reporting.

“Of course I smash my knuckleball finger and my nail falls off,” Johnson said, referring to his index finger. “I show up to spring training and they want me to do it, and I can’t because I don’t have a fingernail yet.”

Johnson, a right-hander, did collect pointers on the knuckleball from the Blue Jays’ R. A. Dickey, and now he is putting some to use. He is learning to keep his pitching arm from pulling past his lead leg when he releases the pitch. A knuckleballer should try to come straight down in his follow-through, Johnson said, to kill spin.