Keates, who had seen his side go undefeated in all away league games before Saturday's defeat, admitted that the Saddlers didn't turn up as goals from Glen Rea and Jorge Grant saw the Hatters home to victory.
The Saddlers went into Saturday's clash on the back of a weekend off and looked to be a little off the pace as their opponents eased to victory, moving above their opponents in the League One table.
Keates, who was speaking via the Express & Star, said; "We are massively disappointed with the performance. We didn’t turn up. It’s as simple as that. That is nowhere near the standards we have set for ourselves.
"The players are low. But when we have lost this season we have had a reaction and that is something we will be speaking about. I’m not one for making excuses. Take nothing away from Luton - they were the better team.
"We’re disappointed for their first goal we’ve conceded from a set-piece. You can’t lose your man. Then for the second, we lose possession, we don’t make the right pass and we give a silly free-kick away.
"We didn’t play on the front foot and we struggled to make an impact all over the pitch. Collectively we weren’t good enough."