While the country may not want rescue loans for its government, it may still approach the eurozone's emergency funds, which would let the ECB to start buying Spanish bonds, keeping a lid on the country's near-term borrowing rates.
De Guindos conceded that Spain was at the epicenter of Europe's debt crisis, which is entering its fourth year. In October 2009, then newly-elected Greek Prime Minister George Papandreou revealed that Greece's public finances were in even worse shape than feared.
"I would even say that the future of the battle of the euro will be waged in Spain," De Guindos told an audience at the London School of Economics.
Earlier, Asian stocks advanced, with Japan's Nikkei 225 index closing up 0.4 percent at 8,863.30 after the Bank of Japan announced no change in the country's key interest rate following a two-day policy meeting.
South Korea's Kospi gained 0.1 percent to 1,995.17 and Hong Kong's Hang Seng added 0.5 percent to 21,012.38.
Markets in China are closed for a public holiday.