The agreement between the USL and MLS about affiliation, wholly owned sides and continuation in the current Reserves system saw four pairs of teams initially launch as affiliates. Seattle Sounders FC is taking a slower approach and trying to figure out the best way to enter this new endeavor. While they are using the Sunday May 12th match in Tacoma as one test they are also talking to Phoenix FC Wolves about going the affiliate route.
On the possibility of an affiliation with Phoenix FC: We're in talks with several different things. Some of the options is to do a team in Washington. There are options in Washington. So there are positives to that. But there are also positives here in Phoenix as well. We're looking at everything and then we'll make a decision.
According to Sounders Sporting Director Chris Henderson (quoted above) the club is checking several options and while there is no timeline the goal is to get into the new Reserve/USL partnership by next preseason.
The goal of the partnership, and whichever route the Sounders take is to get the back end of the roster games. It could also change how the team uses the HomeGrown Player rule. USL Pro also has an Academy Player rule that encompasses MLS' HGPs within it.
There are advantages to using a current team as an affiliate. They have a coaching staff, stadium and all the other things needed to run a soccer team. An increase in Seattle MLS fans in that area would be expected. The disadvantage would be the ease of the coaches for the MLS side to see the players. A team in Tacoma would be able to scrimmage against the Sounders quite simply.
No matter the path taken the new version of the Sounders Reserves (and yes, they could be called nearly anything) will get the players there many more games. The MLS Reserve season is only 12 matches this year and was 10 the year prior. In 2013 the USL Pro season is 26 games per team and is likely to be 28 or more depending on how many join Sacramento as expansion clubs for 2014.
Whether Tacoma, Phoenix, Yakima or somewhere else the shape of Sounders FC's pyramid will be shifting for 2014.