Seattle Sounders have become just the second expansion club to reach the play-offs in MLS history.

Following the brilliant feat of the 1998 Chicago Fire team who managed to not only make the play-offs, but win the MLS Cup, the Sounders now find themselves in a position not many other new franchises have been in.

One man who has experienced success with expansion clubs is Seattle's Peter Vagenas who was a member of the Fire in their first season and 11 years later has helped the Sounders to get where they are now, although he does not classify them as an expansion team.

"Now we're at the point we know anything can happen," Vagenas said.

"We never thought of ourselves as an expansion team. We're certainly not treated as an expansion team by our fans. We're certainly not treated as an expansion team by our ownership group."

Part of the success at Seattle comes down to the quality signings they were able to make in both the expansion draft and luring ready-made players from abroad.

Coach Sigi Schmid outlined this factor as a major player in the Sounders' achievements so far and why it has put them in another league when it comes to other expansion teams.

"I think we checked all the boxes," Schmid said. "You have to make sure you get some quality players from the expansion draft which we did ... you have to do well with your foreign signings which I think we have done. ... I think you also have to get somebody from the draft and we did that.

"Then we signed some good free agents. We were able to check off all the boxes. I think some of the other expansion teams haven't necessarily done that."