The Newcastle striker has apologised after storming straight down the tunnel after being substituted at Middlesbrough.
Martins: "I was absolutely gutted at being hauled off, and it was all down to sheer disappointment.
"Like any other player, I am always most disappointed when I am substituted.
"But I am sorry if what I did was a problem and, in hindsight, perhaps it was wrong for me to go into the dressing room and not go on the bench.
"I was feeling good and felt as though I could score and I still do not know or understand why I was called off.
"I don't suppose it was a surprise that Mark Viduka was brought on, especially as there were no goals.
"But I was hoping I would get the chance to play alongside him and Michael Owen and not be the one to make way for him.
"When the three of us were used together as a three-pronged attack last season we had a fair amount of success."