The backup outfielder entered in the seventh inning in a double-switch, wearing a jersey that read "San Francicso" across the front.
The club said Velez's jersey would be restored to the correct spelling before its next road contest on April 16 against the Dodgers, according to The Associated Press. None of his teammates' jerseys were affected.
Velez told The AP he didn't know anything about the jersey's misspelling.
"No, no, I didn't know," Velez said from the team bus en route to the airport. "That's the first I've heard."
This isn't the first time in recent memory a uniform has had a misspelled team's name.
Last year, the jerseys of Nationals players Adam Dunn and Ryan Zimmerman read "Natinals" for three innings of a game. The jersey manufacturers apologized for the error.
Bailey Stephens is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.