[MLS] The trade of Justin Mapp from Chicago to Philadelphia isn't simply a case of too many midfielders on the same roster, yet that condition surely played a role.

Mapp, 26, in his eighth season with the Fire and ninth in MLS, has gone to Philly in exchange for an undisclosed amount of allocation money. His playing time this season had dwindled, with Baggio Husidic, Peter Lowry and Mike Banner all getting more minutes and Marco Pappa’s emergence as a lock in the starting lineup.

Mapp can compete for a starting spot right away in Philly, which has recovered from a rough start to escape the Eastern Conference cellar yet hasn’t found a lockdown, left-sided midfielder who can give balance to Sebastien Le Toux’s presence.

Mapp started only six of 10 matches for Chicago this season under new coach Carlos de los Cobos, who will give plenty of time to Mexican speedster Nery Castillo, who can play a variety of attacking roles. The house will be more crowded when Patrick Nyarko recovers from concussion-related symptoms that have kept him out of the lineup since July 3.

Castillo is expected to make his first MLS appearance Sunday when Chicago plays the Galaxy, and Nyarko said last week he hopes to be ready as well. The trade also shaves Mapp's $245,000 salary off the Fire's salary cap; as a midseason addition, Castillo will "cost" the Fire $167,500 in cap space in 2010.

The former member of the U.S. U-17 national team started his pro career as a 16-year-old in 2002 with D.C. United, for which he played just 28 minutes prior to being traded to Chicago in February, 2003. Later that year he played in all five U.S. games at the FIFA U-20 World Cup; he had represented the U.S. U-17s two years earlier at the world championship. Mapp earned his first senior cap for the U.S. in 2005 and played all three Copa America matches in 2007.

In three seasons (2005, 2006, 2008) he recorded an MLS personal best of eight assists. Last year, he played 21 games (11 starts) for the Fire, scored one goal, and contributed three assists. In his career he’s played 177 regular-season games with 14 goals and 36 assists.