Striker Jozy Altidore was dropped from US coach Jurgen Klinsmann's Gold Cup squad Tuesday while defender DaMarcus Beasley was added as the unbeaten defending champions prepare for the knockout stages.

The unbeaten Americans, who made three roster changes in all, face a quarter-final match Saturday at Baltimore against a yet to be determined opponent in the biennial North American regional championship.

Altidore, a forward for Major League Soccer's Toronto FC, has been nagged by a hamstring injury and did not play in a 1-1 US draw with Panama on Monday. He started the first two group matches but was removed in the second half of each.

"We believe that Jozy is just not there yet," Klinsmann said. "Jozy never really got into this tournament and never really picked up the rhythm. He's just simply not in the shape right now to help us.

"For Jozy it's just simply going back to Toronto, picking up his rhythm, getting in shape, working on his fitness and then he will start scoring goals again."

Altidore indicated it was an amicable split in a Twitter posting.

"Always a pleasure to be a part of @ussoccer," Altidore tweeted. "all the best to the boys the rest of the way! #KeepTheCup."

His roster spot was taken by Alan Gordon, a 33-year-old striker who has four goals this season for the MLS Los Angeles Galaxy.

Beasley, a 33-year-old defender for the MLS Houston Dynamo who had declared his international retirement last year, replaced Greg Garza, whose first cap tied the Mexican-American to the US roster, while Joe Corona, a 25-year-old midfielder for Mexican side Veracruz, replaced midfielder Alfredo Morales.

Beasley has 121 caps, making him the most experienced player on the US roster. The four-time World Cup veteran last donned a national team jersey at last year's finals in Brazil and now makes his sixth Gold Cup appearance, having been part of four Gold Cup winners, including as captain of the 2013 squad.

Gordon and Corona were also members of the 2013 US Gold Cup winners, with Corona scoring twice in the event.

Klinsmann had 24 hours after the Panama match to make up to six changes in the 23-man roster for the remainder of the Gold Cup.