The new Hoops midfielder, who has scored six goals in 10 outings since joining from Derby County in January, says the players of the Glasgow club now need to deliver the league title to Lennon after losing the Co-operative Insurance League Cup to arch enemy Rangers on Sunday.
Celtic are still in the hunt for the Scottish Cup and the Premiership and Commons has stated that the team will do what they can to redeem themselves.
"The gaffer was bitterly, bitterly disappointed after the final. He was a wounded man,” he told SunSport.
"We let him down without a doubt - 100 per cent.
"There were a few players, including myself, who didn't play to their potential and we let ourselves and the fans down.
"From the manager's point of view we let him down by not doing our job.
"You are expected to be 110 per cent every game and it's demanded you win every single one.
"We're still confident. Our main thought is winning the league and the Scottish Cup and we'll do our utmost to do that.”