Sources: Philadelphia Union acquiring Chris Pontius from D.C. United

The Union have begun their roster transformation process by adding the veteran midfielder, sources confirmed to Goal USA

Chris Pontius spent seven seasons playing for D.C. United, but his run as the club's longest-tenured player is coming to an end as he prepares to start a new chapter of his career not too far from where it began.

D.C. United has agreed to trade Pontius to the Union, sources confirmed to Goal USA. The deal is believed to be in exchange for allocation money and is expected to be announced next week.

The trade ends Pontius' seven-year run at D.C. United, which saw him register 31 goals and 17 assists in 152 matches over seven seasons. The seventh overall selection in the 2009 MLS SuperDraft, Pontius has seen Injuries mire his past three seasons. He missed most of the 2014 season after undergoing hamstring surgery.

Pontius, 28, returned in 2015, but managed just three goals and one assist, playing 23 matches.

The Union will be hoping Pontius can recapture the form that helped him record 12 goals and four assists in 2012. A left-sided midfielder capable of playing in a 4-4-2 or 4-5-1, Pontius could also give the Union an option as a left-sided forward in a 4-3-3.

Pontius may not be the only long-serving D.C. United player to leave the club this winter. Standout midfielder Perry Kitchen is out of contract and far from a sure bet to re-sign with D.C. His MLS rights are held by D.C. United, but he is free to sign outside of MLS, with a move to Europe a very real possibility.