The former New York Home Grown Player is the latest addition to the Union.
Kassel played mostly at right back for the Union during the preseason and impressed the coaching staff enough to gain a highly contested roster spot.
He spent last year with the Pittsburgh Riverhounds, scoring six goals and assisting on two more playing out of a central attacking midfield role.
Signed by the New York Red Bulls as a Home Grown Player, along with fellow academy standout Sacir Hot, Kassel failed to see the field more than twice and was let go by the club without much team fanfare. The New York fanbase, however, was upset by the decision (via Empire of Soccer).
Kassel was the subject of controversy at the start of the 2012 season as he was unceremoniously cut by the team during preseason. This sparked outrage amongst the team's supporters who were already wary of the former regime's preference to hire foreign talent over domestic products.