Doctors initially believed Watson-Siriboe had injured his meniscus, a team source said, but it appears now to be a more serious ACL injury. The extent of the injury and the amount of time Watson-Siriboe might miss was not immediately clear.
Whatever happens could impact RSL's activity when the transfer window opens next month.
"If both of them were to be out for an extended period, we'd have to look at possibly some reinforcements," RSL general manager Garth Lagerwey told ESPN 700 on Wednesday. "We obviously have a lot of confidence in Carlos Salcedo and Aaron Maund to get a job done, but we'd have to look at what is our plan for the rest of the season."
The team will continue to be cautious with Schuler over the next two to four weeks, hoping to prevent the onset of a stress fracture, an injury that kept him out for four months last year.
• Aaron Falk