The 27-year-old returned to his boyhood club on a temporary deal at the start of the season, but remains unsure what the future holds with one more year left to run on his Saints contract.
Clasie has scored one goal in 29 Eredivisie appearances for the club this term, but his chances of making the move permanent are unclear, with Jaap Stam set to replace Giovanni van Bronckhorst as coach this summer.
"Of course my future plays a part in deciding my mindset," he told De Telegraaf.
"Not directly during the matches, but subconsciously outside the competitions.
"Right now I would just want to focus on conquering third place with Feyenoord. I want to close it here as well as possible.
"I don’t have any say in what will happen to me after that. But of course I am playing for my future, there is that realisation."
Saints shelled out £8 million for the Dutchman’s signature in 2015 and he has made 49 appearances for the St. Mary’s club, scoring twice.
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