The Republic of Ireland captain slammed the Galaxy's poor performance after slumping to a 1-0 defeat against the Colorado Rapids.
Vicente Sanchez's 20th-minute goal was enough to give Colorado maximum points, with Keane spurning an opportunity to draw matters level as he missed a penalty midway through the second half — his second penalty miss of the season.
Speaking after the game, the Republic of Ireland international said that Galaxy looked "very sluggish" and "lackadaisical," concluding that it was "probably one of the worst" performances from the team since he joined the club from Tottenham Hotspur.
"We certainly didn't deserve the ending of the game, I don’t think. I think that’s probably one of our worst performances certainly for a long time," Keane was quoted as saying by the club's official website.
"We looked very sluggish and didn’t look like we could get the ball down and pass," he continued. "Sometimes you can have possession just for the sake of having it, so there was no penetration. We just looked very, kind of lackadaisical. It was a poor performance and probably one of the worst since I’ve been here anyway."
The result means that Galaxy remain on eight points in MLS Western Conference with just two victories in their opening six games.