Skrtel had a very good season 2011/12, but I wouldn't say he ever got above decent the rest of the time. Certainly an intimidating fucker though. Last season was a bad one for everyone in our defence, and yet at times we were solid. It was odd. Second highest clean sheets, hardly conceded once, joint-highest in conceding two in a game yet rarely three times. We seemed to improve as the season went on though. For a time Agger simply forgot any sort of marking or positional sense.
As for Coates I have no idea. I always thought he's looked decent most times I've seen him, and even thought he was good with his feet despite being 6ft 5. But he had an utter shocker against Oldham which seems to have sealed his fate. And reading between the lines with Rodgers' interview last month, he's as good as gone. We do have a few youngsters who will hopefully make a bit of a mark next season though, in Wisdom, Kelly and Robinson, though it wouldn't surprise me to see any/all go out on loan.