Goalkeeper Kasey had to watch USA's heroics from the bench as coach Bruce Arena opted to go with Blackburn's Brad Friedel as his number one.
That was a huge blow for Kasey, who seemed to put himself in the frame after captaining the side to CONCACAF Gold Cup success in January.
Instead he was reduced to a supporting role as Arena's men went all the way to the quarter-finals.
Kasey will now take a break from football but is already looking ahead to the start of next season.
"I couldn't be more motivated to getting back on the field," said Kasey.
"I'm looking forward to it. I'm taking a break now but when I come back I'll be raring to go again."
On reflection, Kasey admits USA were bitterly disappointed to go out as they did against Germany in the quarter-finals. They had the better chances but were ousted by Michael Ballack's strike.
"We'd rode our luck on a couple of occasions but ironically we played very well against Germany," he added.
"We let ourselves down against Poland but got another chance, did fantastic against Mexico and had the chances against Germany, but didn't take them. Then there was the handball, but that's football.
"We were happy with how it went overall. Hopefully we've done the game a lot of good back in the States."
Kasey Keller says he couldn't be more motivated for the start of the season after his personal disappointment in the World Cup.