The Scotland international has been one of the best keepers in the Premier League this season which has prompted suggestions of a summer move to Tottenham.
Rumours have circulated that Hugo Lloris could leave Spurs for Paris Saint-Germain at the end of the season with Marshall set to replace the France number one at White Hart Lane but the former Celtic and Norwich City man says he is only thinking about Cardiff.
"I am desperate right now to try to help keep this club in the Premier League," he told Wales Online.
"At this moment in time my personal career does not really come into it. I am going to be judged over these last games now.
"That's me, all the other players and the club as a whole. I will be concentrating now on keeping Cardiff up. We've got a huge game coming up against Crystal Palace (on Saturday).
"The focus is on that and getting the three points. That is the main aim right now."
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