The Scotland international has been one of Cardiff's most reliable performers in a difficult first season in the Premier League for the Welsh outfit.
Poor results on the pitch have left Cardiff three points adrift of safety, while off-field turmoil - including the controversial dismissal of former manager Malky Mackay - has also contributed to a frustrating campaign for supporters.
Marshall's top-drawer performances have been a rare highlight, and his form has reportedly caught the eye of Tottenham, who are believed to have sounded the 29-year-old out should Hugo Lloris depart in order to play in the UEFA Champions League.
However, the former Celtic goalkeeper is only interested in Cardiff's battle against the drop at present.
Speaking to Wales Online, Marshall said: "I am desperate right now to try to help keep this club in the Premier League.
"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."
