One & Only

[KCGHOST]

Scott Sheldon and Kevin Seitzer are the only position players to have ever done this.

[Honus Wagner]

sheldon is one of four players to play all 9 positions in a game--he did it in the shortest inning span from the 5th inning to 9 inning

sheldon and seitzer played all 9 positions at some point in career...they also just faced 1 batter and struck him out

[Utter Chaos]

...they also just faced 1 batter and struck him outI'm willing to bet that's the answer.

For the record the two players were Jeff Leifer (by Sheldon) and Carlos Martinez (by Seitzer). Actually Seitzer struck out Glenallen Hill but it was charged to Martinez. I believe Downs was pitching to Martinez and in the middle of the at bat Oakland switched pitchers and Cleveland switched batters but I haven't been able to confirm it. If that's the case than Seitzer struck out Martinez without even pitching to him!

[KCGHOST]

Sheldon is one of four players to play all 9 positions in a game-

Clearly if he is one of four then Seitzer and he cannot be the only ones to have done it.

Sheldon and Seitzer played all 9 positions at some point in career

I can find no record of Seitzer having caught.

They also just faced 1 batter and struck him out

They are the only position players to strike out everybody they pitched to.