Honestly, I think people overrate our lefbacks to crazy levels. Kolarov can cross the ball brilliantly and maybe once a season will stick a freekick in, but other than that he is a poor player. Defensively he is terrible, if anyone ever attacks down his side we are in trouble, but not only does he not do his job well he makes the LCB's job incredibly difficult as they have to cover for him.
Then we have Clichy, who is a complete non-entity going forwards 95% of the time and defensively is barely average. He's played to be the more solid option, but that's more a criticism of Kolarov than a compliment to Clichy, as he cannot be relied on at all to defend. He frequently goes to sleep and lets people in behind him. He goes through patches of being decent, but then goes through patches of being a complete liability, he's nowhere near consistent enough to be considered the reliable one.
Neither of them are good enough for a side that wants to be doing well in the CL. They are the serious weakness in our side and teams target them and take advantage.