Halfway through the 2004 Vuelta, it appeared it would become an easy win for Heras, but in the last week his fellow countryman Santiago Pérez won two heavy mountain stages, thus becoming an important rival.
Halvvejs gennem Vueltaen i 2004 så det ud som en nem sejr for Heras, men i løbets sidste uge vandt hans landsmand Santiago Pérez to massive bjergetaper, og blev dermed en vigtig konkurrent.