A Rapids team that has endured an abnormal epidemic of injuries this season suffered its biggest blow today with the news that forward Conor Casey is done for the season with a torn left Achilles tendon.

Casey was injured in the first half of Saturday’s game at Seattle, and an MRI was performed Monday, detecting the rupture. Casey is scheduled for surgery Wednesday, and his recovery is expected to take eight months.

Casey is the team’s leading scorer, having scored six goals in seven preceding games before the Seattle game.

“I’m bitterly disappointed for Conor,” Rapids coach Gary Smith said. “He was in a terrific run of form, his goal return (ratio) to games is quite phenomenal. For us and him, we’re going to miss each other.”

Smith raised the possibility that a temporary playing field at CenturyLink Field caused the injury. Seattle normally plays on synthetic turf, but the club laid sod recently for Wednesday’s “friendly” with Manchester United. The field was slow, heavy and unfirm.

“Honestly, the surface was dreadful, absolutely dreadful,” Smith said. “The grass was too long, to cover the seams. It rained early in the morning heavily, and there’s no drainage because there’s plastic underneath. It wasn’t only spongy, it was like running in treacle (molasses).

“Can we relate (Casey’s injury) to the pitch? I think so. I think the pitch moved. There’s no stable foundation to that turf. It’s heavy, it puts an added stress on players’ bodies. Can we categorically say it was the pitch’s fault? I don’t know how we prove that.”

It doesn’t much matter now. The Rapids have to move on.

“For the sake of the team, you try to put it past you and move on,” said fellow forward Omar Cummings, who formed a lethal partnership with Casey up front in last year’s run to the MLS title. “I know that’s what he would want, for us to push on and do the best we can. But as a teammate and a friend, you feel for him. To see him be out of the team, it’s a blow.”

John Meyer: 303-954-1616 or jmeyer@denverpost.com