Union forward-midfielder Sebastien Le Toux suffered a concussion in Wednesday's 2-1 Round of 16 U.S. Open Cup win over the New York Red Bulls and won't be available for Saturday's Major League Soccer game in Houston against the Dynamo.
Le Toux hit his head in a collision in the 79th minute and left the game. He played up top because the Union's top two forwards, C.J. Sapong and Fabian Herbers, were out with injuries.
Le Toux has not missed an MLS game this season for the Union, appearing in all 17 and starting 12. He has two goals and a team-high five assists.
Sapong hasn't played since June 1 due to a sprained right ankle, but coach Jim Curtin said after the game that he expects him to be a "factor" against Houston. Herbers remains day to day with an injured right hamstring.
The Union (7-5-5, 26 points) are in first place in the Eastern Conference, while Houston (3-8-5, 14 points) is in last place in the Western Conference. Despite its record, Houston beat Sporting Kansas City, 3-1, in Wednesday's Round of 16 U.S. Open Cup game. Sporting Kansas City is the defending Open Cup champion, having defeated the Union on penalty kicks in last year's final.