Hearts beat Scottish Premier League champions Celtic 1-0 on Saturday with Lafferty scoring the only goal. Lafferty has claimed his performance has been helped by the fact Steven Gerrard's Rangers made an offer for him.
The 'Gers' had an offer of £200,000 rejected by Hearts last month for the striker.
After bagging the winner against the 'Bhoys', Lafferty said: "Hearing teams like Rangers are interested in you, you tend to give that little bit extra.
"To show that I can play and that I can score goals. I will keep on concentrating on myself, doing well for the team and being involved in as many good results as possible.
"Rangers' interest is something you have to look at and you know you're doing something right.
"But it's up to the two clubs. I owe Hearts the respect to continue giving 110 per cent. If something happens, it happens but it's out of my hands.
"I am working hard, playing in games, getting results like today and enjoying football."