HOUSTON — U.S. national team forward Brian Ching left the Houston Dynamo's home opener because of a strained left hamstring, an injury that could hamper his preparations for the World Cup.

Ching, a 31-year-old Kamehameha alum from Hale'iwa, sprinted toward the goal in the 30th minute, went down, reached for his leg and was carried off the field. Dynamo spokesman Lester Gretsch said the team probably would not know until Friday how long Ching will be sidelined.

With Sochaux's Charlie Davies out since October because of severe injuries sustained in a car crash, the U.S. is uncertain who will start at forward alongside Hull's Jozy Altidore. Ching and Colorado's Conor Casey have been competing to make the roster as forwards.

Ching made his national team debut in 2003 and has 11 goals in 44 international appearances. He was on the 2006 U.S. World Cup roster but didn't play during the tournament.

Ching was replaced in the game by Luis Angel Landin. The Mexican forward was signed by the Dynamo last August on loan from Cruz Azul as a high-priced "designated player" but hasn't started Houston's first two games. He appears to be overweight and out of shape.