David Estrada (Sounders photo) David Estrada (Sounders photo)

D.C. United lost another forward to an injury but acquired an attacker in a trade.

On a day Michael Seaton was ruled out for a month with a strained quadriceps, United received midfielder David Estrada from the Seattle Sounders for 2017 third-round draft pick.

Seaton, an 18-year-old striker who was on the game-day roster the past two matches, was injured in training Wednesday and will miss a month. Two days earlier, reserve forward Conor Doyle underwent season-ending knee surgery.

The trade with Seattle was apparently in the works for some time and unrelated to the injuries. Amid the busiest stretch of the season — eight games in 33 days — United has been in the market for midfield depth. Estrada, 26, plays on the wings and could fill in up front.

The fifth-year pro from UCLA made one league appearance for the Sounders this season — a five-minute stint against United at RFK Stadium. Seattle loaned him to third-division Charlotte twice and second-division Atlanta once this summer.

Estrada’s finest campaign came in 2012, when he scored all five career goals and started 12 times. Overall, he has appeared in 41 MLS matches and made 18 starts.

United also announced it had released rookie midfielder Christiano Francois, a former Maryland Terrapin on a season-long loan with third-division Richmond. The Haitian native arrived with raw technical skills but rarely played for the Kickers.