The Nigerian - officially 32 years old - scored on debut in a 2-1 FA Cup victory over Derby County on Saturday, netting an 82nd-minute winner.
Yakubu, though, has been plagued by doubts surrounding his age throughout his career, but insists he will not allow the issue to affect his form.
"You can see the way I play, so I am not talking about my age," he said. "It is normal. People can choose if they don't believe it, so it's up to them.
"But for me I am just enjoying my football.
"The hunger is always there. When you play in England you always have the desire to play. You cannot hide here."
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