Compared to the rest of his year so far, Wimbledon was hopeful for Marin, but still a far cry from his 2014 campaign, although he both times made it to QF.
Last year he came to QF largely untroubled and gave a very good fight to Djokovic, taking a 2-1 lead in sets even. He just couldn't keep it up in the last 2 sets. This year, he got taken to 5 sets by both, Berankis and Isner and was in real danger to lose especially vs. Berankis who played a great match. Cilic won only thanks to his superior serve which bailed him out at key moments.
He then went on to even lose a set vs. Kudla. He faltered badly vs. Djokovic, a disappointment of a match that failed to deliver in every respect, but maybe not unexpected, when considering how many hours he had clocked on the court already prior to that meeting and the physical challenge of playing Djokovic.
So I think, it's possible that he regains form until US Open, since there is still time left, but it's highly unlikely.