Just out of interest how much time do you think Andy needs to get comfortable on clay? Lets forget the 7 clay court season he's played since becoming a pro, he spent 3 years playing on clay in Barcelona when he was younger. Think about it. That's 3 years. Not 3 days. Not 3 weeks. Not 3 months. THREE years! When you grow up you learn to ride a bike. You may not ride it again for another 20 years but you will remember all right.
In my opinion if Andy is not comfortable on clay by now he will never be comfortable on clay and he will just have to accept that and make the best of a bad situation which to be fair is probably what he is doing.
But it's not as if Andy forgot to ride. He knows how
to ride. The question is, can he ride well enough
I think it has more to do with Andy’s priorities. All this time he had this priority going on that, he needed to win a Slam as he’s been constantly a top 4 player. And it goes without saying that his best surface has always been either grass or hard (or both) and a Slam would come on either of those two surfaces first. So obviously he had to pay a lot more attention to those events played on grass and hard. Clay got sidelined in the meantime. But that will change once Andy gets Wimbledon under his belt because that will only leave RG and he can then set his priorities accordingly. Lendl is the right person to train him on clay and take the next step.
And Andy did not spend 3 years in Barcelona to take the world by storm by winning one RG after another, but because he probably wasn’t nearly as good as he is now on clay back then and so he needed to practice on it, so that he could compete at least on average level.
Andy’s game on clay is better off than Sampras keep in mind and he still won 3 clay titles including Rome and reached the RG semi in 1996. He beat quite a few great clay courters and past FO champions at that too. So Andy can definitely take it to much higher level on clay as his game is better suited than Sampras on clay.