"It was a disappointing result," Griffiths said in an interview with UKAthletics. "But it was good to get on the field and try and get a goal there at the end. It was good to be there.
"It has been kind of hectic, graduating from Kentucky at the end of May," he added. "I played in the Benfica game (May 19) and then came back from my trial a week later. It is good to be here playing professionally and hopefully we can win some games and get rolling."
Revolution vice-president of player personnel Michael Burns added: "We're pleased to bring Jason into the squad. He's a hard-working central midfielder who we believe can grow in our system."