Long has scored seven goals in his last six games and has been linked with a move to West Ham but McDermott has no doubts he will stay after he scored the winner against West Brom in the FA Cup.
He said: "I know this will bring more attention on Shane but as far as I am concerned he is staying.
"I have a great relationship with him and now he is getting rewards for his hard work.
"He is a great character and the goals are coming.
"I fielded a strong team because my priority is to win whatever the competition."