Speedy right winger Joshua Gatt won't get his chance to impress Jurgen Klinsmann in person at this year's Gold Cup. After being called up to the squad, he suffered a knee injury in a league match for his club team, Molde. That injury is serious enough that he will be replaced in the Gold Cup squad, according to Soccer By Ives.
As Ives noted, Gatt has had very bad luck with the timing of his injuries. He was forced to miss a World Cup qualifying in September and Olympic qualifying a year and a half ago because of injuries he suffered just prior to those matches.
Because the Gold Cup features mostly fringe USMNT players, Gatt likely would have had multiple chances to play in the competition. Joe Corona looks like the most likely starter at right wing for the U.S., though Alejandro Bedoya has played there in the past. More recently, Bedoya has transitioned into being a second striker.
Brad Davis, Brad Evans, Benny Feilhaber and Graham Zusi are the midfielders on the Gold Cup preliminary squad that are eligible to replace him. Brek Shea is also eligible, but is injured. Bobby Wood, Alan Gordon, Eddie Johnson, Carlos Bocanegra, Omar Gonzalez, Matt Besler and Tally Hall are the other players eligible to be added to the roster.
Feilhaber is the only midfielder on the list who is healthy and who has not been taken away from his club for USMNT games so far this season, so he's my bet to replace Gatt on the roster. There's also a chance that Klinsmann decides to wait until the knockout stage to make any additions to the team, which he is allowed to do. At that point, a player who has participated in World Cup qualifying (like Zusi or the Brads) could be added to the team.