Killie posted their first victory at Parkhead in 57 years as the much-changed hosts stumbled on Saturday and the 29-year-old has blamed his team-mates' attitude for the defeat
The Hoops made several changes for the SPL clash, having suffered a heartbreaking last-gasp 2-1 defeat to Barcelona in the Champions League on Wednesday.
But, despite the presence of fresh legs for the hosts, goals from Cillian Murphy and Liam Kelly gave Killie a famous victory at Parkhead - and Commons has criticised Celtic's approach to the game.
|9/4||Celtic's Gary Hooper is 9/4 with Bet365 to be the SPL's top scorer this season
"Our attitude wasn't right from the start and it's hard to put into words why," he said to Sky Sports.
"I think playing for a club like Celtic you need to get some middle ground of what's required in a game, whether it's Camp Nou or in the SPL.
"You can't expect to play so well in one game and then put in that sort of performance, in two games we've gone from one extreme to the other.
"We've gone from being really good defensively, everyone working hard off the ball, and everyone wanting to help each other to looking like strangers out there - looking like lost boys.
"I know a few came into the side, myself, James Forrest, Beram Kayal, Miku and Adam Matthews, but we've been playing together for years now so it should just click together.
“Once one goes in, one goes out, and it should slide in nicely but we looked like a lost team.
"The manager was bitterly disappointed and he obviously wasn't happy with the performance or our work rate.
"There was no desire to win the match and we as players demand a performance that's acceptable, but obviously everyone was unacceptable against Kilmarnock."