Chris Pontius, left, will miss four to six additional months after having a second surgery on his left hamstring. (Katherine Frey/The Washington Post)

D.C. United midfielder Chris Pontius will miss an additional four to six months after undergoing surgery on his left hamstring for the second time since the end of last season.

Pontius, an MLS all-star two years ago, missed United’s first six games and on the current timetable would probably not return until the final portion of the 34-game schedule.

Michael Gerhardt, the U.S. national team’s physician, performed the latest surgery.

Pontius, who will turn 27 next month, underwent surgery in November, with a recovery time of six to eight weeks. He joined the club in Florida for training camp but returned home early because of nerve issues. Since the initial surgery, he has required minor procedures to remove scar tissue.

Injuries have hindered him several times during six-plus seasons in MLS, the longest current tenure on United’s roster.

In September 2010, Pontius had season-ending surgery on his right hamstring. Almost exactly one year later, he fractured his right tibia and missed the rest of the campaign. In 2012, he enjoyed a career-best season with 12 goals, four assists and selection to MLS’s all-league team. Last year, with injuries restricting him to 22 regular season matches (19 starts), he never seemed at full strength in posting two goals and three assists.

Chris Rolfe, acquired three weeks ago from Chicago, is Pontius’s long-term replacement on the left wing.

Meantime, goalkeeper Bill Hamid has recovered from a toe injury that sidelined him for three matches. Coach Ben Olsen would not say whether Hamid or Andrew Dykstra (one goal conceded) would start Saturday night against FC Dallas at RFK Stadium.

Midfielder Luis Silva, out for three games with an ankle injury, and defender Chris Korb, sidelined since preseason with a knee ailment, should be available Saturday, Olsen said.