Moreno wins penultimate stage in Burgos
Moreno powered to an impressive win on the hilltop finish of the 168km stage from Roa de Duero to Ciudad Romana de Clunia, holding off Euskatel's Samuel Sanchez on a day when Spanish riders occupied the first three positions.
Saturday's stage winner paid tribute to team-mate Rodriguez after his victory.
"I have to thank Joaquim for the big help he gave me in the crucial part of the stage," said Moreno.
"Without his help, probably today I couldn't have won. Tomorrow all of us will try to help our leader in order to defend his leadership. If we manage to, this Vuelta a Burgos, for Katusha, will be incredible."
Rodriguez enters Sunday's final stage seven seconds ahead of Movistar's David Lopez and eight seconds ahead of Movistar's Pablos Lastras.
Fourth stage results
1. Daniel Moreno Fernandez (Spa) Katusha Team
2. Samuel Sanchez Gonzalez (Spa) Euskaltel-Euskadi
3. Pablo Lastras Garcia (Spa) Movistar Team
4. Ricardo Garcia Ambroa (Spa) Orbea Continental
5. Juan Jose Cobo Acebo (Spa) Geox-TMC
6. Joaquím Rodríguez Oliver (Spa) Katusha Team
7. Stefano Garzelli (Ita) Acqua & Sapone
8. David Blanco Rodriguez (Spa) Geox-TMC
9. Yukihiro Doi (Jpn) Skil - Shimano
10. Denis Menchov (Rus) Geox-TMC