The 23-year old Colombian missed the 2-2 draw with San Jose Earthquakes last week because of a wrist injury which required surgery recently and it seems highly likely that he will not be right for the home clash with the Fire, currently placed fourth on the Eastern Conference table.
Sounders coach Sigi Schmid said that Montero would be most likely not be risked as his side tries to improve on their sixth place in the West.
"The chance of him playing on Saturday is unlikely at this stage because there is still some swelling in there," he said.
"They want to make sure that there is still no infection into the wound. He's able to do some light stuff, and we had him out here doing a little bit of stuff before, but right now unless there is a miraculous change tomorrow it doesn't look likely."