In May of 2021, I decided to seek out an address for Erik Johnson. I discovered that he owned a college baseball development program in California, so I sent him my card and the following letter.
125 days later my card came back signed and he included a brief note.
Erik signed a 1991 Line Drive AA Pre-Rookie card #309.
https://www.baseball-reference.com/players/j/johnser03.shtml