The Germany international midfielder has spent the entire 2013/14 campaign in Spain after being deemed surplus to requirements at Stamford Bridge.
Chelsea's first team ranks are loaded with creative influences, and Marin is among those who find themselves on the fringes of the fold.
He has also struggled to hold down a regular role during his time in La Liga, but has taken in more game time than he would have got in England.
Marin must now decide what his next move will be, with a long-term contract penned in London following his arrival from Werder Bremen in 2012 due to run for another three years.
He told Deutsche Presseagentur: "Nothing has been decided yet. We will sit down and discuss things at the end of the season.
"Sevilla would like to keep me here, but there are also signals from England that they (Chelsea) want me to return.
"So far I have never really had enough fitness. I have started to play more regularly in the last few weeks, but I still can't play three matches per week.
"I have been unable to feature regularly for my club and unable to put out my best performances in matches.
"I always knew that I wouldn't be able to take part in the 2014 World Cup, but my aim now is to regain full fitness."