The Scottish giants held Pep Guardiola's side to a 3-3 draw in the Champions League on Wednesday night, ending a 10-game winning run under the Spaniard.
Former Arsenal captain Keown was asked in a Daily Mail Q&A, 'Does failing to beat Celtic prove that Manchester City are not invincible under Pep Guardiola?', to which he responded: “Manchester City's draw at Celtic is a chink of light for every other team in the Premier League.
“City showed signs of problems at the back against Swansea last weekend. Swansea did well in the game but lacked the finishing quality that Moussa Dembele showed on Wednesday night.
“It shows that City are still a work in progress and Pep Guardiola will be working hard to get it right.