He featured just 15 times in all competitions, as poor form and injury problems cost him a place in the first-team.
This summer, with Willian, Kevin de Bruyne and Andre Schurrle now at the disposal of new boss Jose Mourinho, his time looked up.
However, at 24-years-old, Chelsea would be remiss to give up on him just yet - so instead they sent him out on loan to Spanish outfit Sevilla.
He has impressed in Spain so far - so much so that last month the clubs fans made it clear they wanted to keep the tricky winger in Spain next season.
It was to some a surprise to see that Marin struggled in the Premier League, while others suggested he was always not cut out for the physical rigour of Premier League football.
Form was one part of the problem, but in the end it was his fitness issues that were one major part of his failure in London.
The main problem was a hamstring strain that plagued him at the start of his Chelsea career, meaning he failed to get fully off the ground. That niggling injury continued for most of the season - and he would have hoped those times would be behind him.
But the news today confirms that Marin is once again suffering from a similar problem - which is set to leave him on the sidelines in Spain for up to four weeks.
While the strain is not said to be serious, neither was the problem he had last term, but it stayed with him for the majority of the campaign.
He will now hope to recover fully from this latest setback in order to have an impact at the Sanchez Pizjuan and either earn a permanent move or second chance at Chelsea.
So he must hope that hamstring trouble does not put his season on the skids for a second term running.
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