The Seattle Sounders lost Osvaldo Alonso and Roman Torres to injury in the team's 3-0 win over the Vancouver Whitecaps on Wednesday.
Midfielder Alonso and center-back Torres were subbed off in the second half of the match.
Alonso has been diagnosed with a quadriceps strain, while Torres is believed to have a knee or groin problem.
"They're tough kids," Seattle coach Brian Schmetzer said after the match. "It'll be day-to-day on Roman.
"Ozzie has a strained quad, but what he proved last year...