Ever is a very long time and Murray is still quite young but for such a fine player who has been at the very top for so long his records on clay are surprisingly poor. Pretty much as soon as he gets a decent clay player he loses. IMO he's outside the top 20 on clay and unless he tries to vulture a weak 250 I see little hope he'll capture a title on clay.
In fairness he has had some pretty good results on clay.
If you go back to 2011 he made the SFs of Monte Carlo (lost in 3 to Rafa), Rome (lost in a 3rd set tie break to Novak) and the French Open (lost to Rafa is straights but was competitive throughout). Madrid where he lost to Bellucci in R3 was his only poor result.
Since then he has clearly not done so well but has obviously had back problems playing on the surface. If the operation allows him to get back to 2011 levels on clay he has a chance of winning something.