Barkley's played plenty. Distin played plenty up until the new year and Coleman has sadly been dross for most of this season. Baines at least can create something, Coleman's looked a shadow of the player he was last season.
I'm also forgetting all these goals he's been at fault for.
Don't think Coleman's been "dross." I think we all have a tendency to rate our best players like Baines and Coleman against what we know they're capable of, while looking at unproven players more charitably. Coleman has had a fine season for a right back in absolute terms, very few defensive errors, wins several corners a game, etc. We've relied on our fullbacks much less often this season, I'm guessing because we've been bleeding goals so keeping them out became the priority for Baines and Coleman. Now that we look a bit better defensively, the shackles seem to be coming off our fullbacks (both young boys legs, and against Leicester, the focus was on getting the ball to Oviedo/Luke and Coleman high up the pitch in a way we haven't seen much of this season).
I think Coleman had an unreasonably good season last year, very few fullbacks in the world can score for fun like that, and I don't think that should be the benchmark for evaluating his future performances.
Now that he seems to have license to venture forward more often, I think we'll see the offensive side of his performances improve as well.