I have a feeling it has something to do with Memoria... The 'I' could be for example the Defense Phantom, the answer being... Hmm... the Ribbon card?
Reach for the stars
And your dreams will come true,
When you find him and challenge him, Zidane looks up as if the Phantom was "in the stars".
I could be a coward,
but only to you,
He plays his game very defensively and does not really attack
I may not be strong,
but my talent I gain,
Again he plays defensively (and his cards are defensive)
I say who I am,
but thats not what you need,
If my memory servs me right, he says: "I am the Defense phantom" or something like that. His name isn't the answer though.
The answer is there,
but on time do not heed.
The answer (Ribbon card) is always in his hand. "On time do not heed" may refer to that you can take your time with the game
Ribbon card being "gotten from him" as you say.
Doesn't sound right anymore, but since I typed it out I might as well post it