After losing veteran midfielder Justin Mapp to the Montreal Impact in the Expansion Draft, the Philadelphia Union claimed fellow midfielder Nizar Khalfan from the Vancouver Whitecaps in the Waiver Draft.

The Union also released central defender Juan Diego Gonzalez and goalkeeper Thorne Holder. Waiving Gonzalez and Holder opened up two international roster spots, one of which was needed to acquire Khalfan.

Khalfan is a Tanzanian international, having represented his country in 25 officially sanctioned FIFA games, scoring five times. The 23-year-old's time with the Whitecaps wasn't nearly as successful as his international career, spending 48 games between Vancouver's USL and MLS editions, scoring only three times. He potentially fills in directly at left midfielder for the departed Mapp, but worries about his endurance make him more likely to be an impact substitute later in games.

Each of the Union's two released players did not see the field last season. Gonzalez and Holder both spent time either not being included in the team's game day squad of 18, or with the medical staff.

Holder was hampered all season by multiple injuries, including a couple of concussions. The former Trinidad and Tobago youth international started the season off as the Union's second string goalkeeper, but injuries and strong showings from fellow rookie Zac MacMath in practice pushed Holder down the depth chart. Late in the season, Holder was injured against the Columbus Crew in a reserve game and did not return from it. Emergency goalkeeper Chase Harrison joined the Union, taking the role of back up while Faryd Mondragon recovered from surgery on his right ring finger.

Gonzalez was signed in August of 2010 and made a few starts for the Union, but was quickly relegated to the bench, where he was seldom seen by the end of the 2011 MLS season. The 31-year-old has had a hard time settling with any club during his 14-year soccer career, playing with 10 different teams over that span, none for longer than two seasons. The Colombian center back made around $193,000 in guaranteed compensation last season, making him one of the worst values in MLS.