Andy simply hasn't had enough tour matches since being out since September, especially against top players. First one he had was Federer, and Murray said it was a shock to play him. Cilic is not necessarily a top player, but he is hot at the moment. Hardly anyone can come back after a layoff with miraculous play like Nadal did last year after so few matches.
This is normal... not really anything to be upset about. Andy needs more tough matches like this. Big picture? He needs to be ready by Wimbledon.
Respectfully,
masterclass