The now-retired Sounders legend and current TV analyst was at a loss to explain Seattle's fluctuations in form.
And even he can't figure out what was up with the Rave Green this year.
"It was crazy," Keller told Goal USA, speaking via phone in his role as a spokesman for Castrol. "You see this sometimes in a season, where a team will go through a little bit of a bad spell and maybe a few things go against them or whatever, but it's really, really difficult to explain the wild swings where you win five, six in a row; you lose five, six in a row.
Seattle began 2013 with a five-game winless run. Then there was a five-game unbeaten streak with four wins. That dichotomy -- the bewildering bounce from brilliant to bland and back -- would set the tone for the season. Between July 20 and Sept. 29, the Sounders lost just one game from 12. But the last two matches of that run were draws which formed the beginning of a seven-game winless run -- including four straight losses -- which lasted through the end of the regular season.
After a play-in round win over Colorado, Seattle was embarrassed by archrival Portland in the Western Conference semifinal, a 5-3 aggregate scoreline masking a disjointed and largely underwhelming performance over the two legs.
"I know MLS is a little bit of a different animal in itself," Keller continued, "because of the way the cap works and how close everybody is in the talent level because of the cap situation, but it really is difficult to explain. I wish I had an answer for you, and I'm sure (Seattle head coach) Sigi Schmid wishes he had an answer for you, but it's something the team is obviously trying to rectify.
"I think there are going to be wholesale changes in the squad for next season."
Keller's words were prophetic. Since his interview with Goal, the Sounders have offloaded Mauro Rosales, Marc Burch, Steve Zakuani, Adam Moffatt and Eddie Johnson, while adding Stefan Frei, Tristan Bowen, Chad Marshall, Kenny Cooper, Chad Barrett and Corey Hertzog.
One person who wasn't jettisoned by the Seattle leadership was head coach Sigi Schmid, despite the veteran manager coming under criticism in 2013, and Keller felt the retention was justified.
"I wouldn't have been surprised if they had decided to make a move," he admitted in regards to a potential Schmid firing. "But at the same time, I wasn't particularly surprised that they didn't.
"I think if you look at what Sigi has done -- always making the playoffs, three Open Cup championships, another Open Cup final -- there was comfortably enough success to retain Sigi. At the same time, you're talking about a club that has massive aspirations and wants MLS titles."
To add to the pressure on the club and its manager to deliver, Seattle was the recipient of an unprecedented and controversial piece of league largesse; with financial help from MLS, U.S. national team captain Clint Dempsey joined the Sounders on Aug. 3, in a deal that made him the league's highest-paid player and the the subject of its record transfer fee payout.
"I think sometimes when you have a season with so much opportunity -- when late in the year, you're favorites to win the Supporters' Shield with games in hand and then somehow it all goes wrong, and then you have an exit out of the playoffs against your biggest rival -- yeah, that's when you get a pretty big knee-jerk reaction and say 'hey, we need to blow this thing up.'
"But they decided that because of what he has done, both for Seattle and in the past, that they were going to give him the benefit of the doubt, and get one more year to see if he can put it right."
In 2014, there will be a lot of people -- the Sounders ownership group, the league's most visible fanbase and everyone at MLS headquarters to name a few -- hoping that in his and the team's sixth year, Sigi Schmid can put it right, and finally lead the Sounders to the promised land.