Spain coach Vicente del Bosque says the world and European champions could again line up without a recognised striker against Republic of Ireland.
Barcelona's attacking midfielder Cesc Fabregas played in a more advanced position as Spain drew 1-1 against Italy in their Euro 2012 opener.
"Against Ireland we will play a number nine - though it depends what you understand by a number nine," he said.
"David Silva is a forward; Andres Iniesta plays like one, so does Cesc."
Del Bosque's decision not to start with one of his three traditional strikers - Alvaro Negredo, Fernando Torres or Fernando Llorente - surprised many on Sunday, including opponents Italy.
But the coach said he would not be swayed by the opinions of outsiders.
"We have four options - the three everyone is aware of (Negredo, Torres and Llorente) and then that of Cesc," he said.
"Those are all very good attacking solutions. I am not unhappy with the options we have.
"The only thing that interests us is what is in the interest of the team. The opinions of others surely have interests distinct from our own."
Spain complained about the quality of the Gdansk pitch following their clash with Italy and they decided to train at their practice ground, rather than the stadium, on Wednesday.