Defoe's impact is most likely to be off the bench, using his pace to ruffle a tiring Madrid defence.
"In my mind, I don't really expect the manager to change things because, if it was me and something has worked, maybe I'd go the same way," he told the Telegraph.
"Each game is different, though. You never know what the manager is going to do in Madrid. But if I start getting frustrated, that is when my game would change and mentally you're not right and not focused.
"It doesn't get much bigger than Real Madrid in the Champions League quarter-final and that is why it is important to stay positive. If you start the game you do your best, if you come on as a sub it is important to make an impact. Being a striker, you can always do that."