Young keeper Josh Ford won the third keeper spot this year. In the past the non-starting keepers have been a crowd and cluster with Ford being one of them, but for the next six MLS matches he will not be eligible for the 18. Seattle Sounders FC announced today in a team release that Ford was moved to the MLS Short Term Disabled List with a fracture of his right patella (knee cap).
A player who has a short-term injury can be placed on the Disabled List once another player has been signed as a replacement (provided the team has budget space). The team will remain responsible for the full amount of the injured player's salary on the salary budget. Note: the injured player will have to sit out a minimum of six MLS League matches before he can rejoin the team's roster.
International player limits still apply at the time a short-term replacement is made (with the player being replaced not counting against those limits).
Seattle has two roster spots open at this time, but it would seem one of those will be filled shortly per the above quote. Ford is not restricted by rule from playing in Open Cup or Reserve League matches.