"It's (his hamstring), a slight tweak, and is not as bad as we initially thought," Schmid said. "We wanted to go easy with him today and see where he is tomorrow. There's an outside chance he could play Friday, and for the second game it shouldn't be a problem."
The second playoff game will be on Real Salt Lake's home field in Sandy, Utah on Thursday, Nov. 8.
Johnson, who is a candidate for Major League Soccer's comeback player of the year, felt something wrong with the hamstring in the second half of Seattle's final regular-season match on Sunday. Instead of risking a devastating injury, he asked to come out immediately.
Schmid would not say which player might start in Johnson's place should he not be healthy enough to go against Real Salt Lake in the first leg of the playoff series Friday night at CenturyLink Field. Obvious candidates are Sammy Ochoa and David Estrada.
Schmid was also encouraged about the continued recovery of left back Leo Gonzalez from his strained hamstring, and central defender Jeff Parke, who also sustained a leg injury in the Los Angeles Galaxy game.
While Seattle has been in the MLS playoffs four years in a row, the Sounders have yet to win a series, including last year's disappointing defeat against Salt Lake.
Schmid said his club is on a mission to stop that trend.
"We want to get beyond the first round because we haven't accomplished that," he said. "I think the players are motivated and focused on that task at hand."