The 25-year old forward suffered a ruptured anterior cruciate ligament and damaged lateral collateral ligament in Sunday's 1-0 loss to Portland Timbers at Yankee Stadium and will undergo surgery later this week.
"It's always very disappointing when you see a player suffer a serious injury," NYCFC head coach Jason Kreis said in a team statement.
"Tony is a great young professional, and I know his teammates are going to miss him on the field.
"Everyone at New York City FC is 100 percent behind him in his recovery and will be there to help every step of the way. I know that Tony will receive the best medical support, and I'm confident that he'll come back fitter and stronger than ever."
New York City FC (@NYCFC) April 21, 2015