Race leader Wout Poels solidified his position at the top of the general classification with a solo win at the Volta a la Comunitat Valenciana, with Team Sky teammate Beñat Intxausti coming in second place.
Dutchman Poels held off challenges from Diego Rosa (Astana) and Fabio Aru (Astana) on the final climb to Xorret del Catí and attacked near the summit to sail home by 23 seconds.
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His lead now sits at 46 seconds heading into the final stage on Sunday, with Luis Leon Sanchez requiring a minor miracle to overcome the Sky rider on a flat finish in Valencia.
Intxausti moves up to third overall, ten seconds behind Sanchez, with Rosa, who held third overnight, slipping to seventh overall.
Stage five gives a pretty flat challenge, punctuated by a category three climb at the halfway mark.
Volta a la Comunitat Valenciana stage four, Orihuela-Xorret del Catí (141.3km)
1. Wout Poels (Ned) Team Sky, 3-26-32
2. Beñat Intxausti (Esp) Team Sky, at 23s
3. Ion Izagirre (Esp) Movistar, st
4. Fabio Aru (Ita) Astana, at 25s
5. Daniel Navarro (Esp) Cofidis, st
6. Luis Leon Sanchez (Esp) Astana, at 31s
7. Davide Formolo (Ita) Cannondale, at 38s
8. Sergey Firsanov (Rus) Gazprom-Rusvelo, st
9. Tom-Jelte Slagter (Ned) Cannondale, st
10. Javier Moreno (Esp) Movistar
Overall classification after four stages
1. Wout Poels (Ned) Team Sky, 12-03-26
2. Luis Leon Sanchez (Esp) Astana, at 46s
3. Beñat Intxausti (Esp) Team Sky, at 56s
4. Ion Izagirre (Esp) Movistar, at 1-01
5. Javier Moreno (Esp) Movistar, at 1-10
6. Fabio Aru (Ita) Astana, at 1-26
7. Diego Rosa (Ita) Astana, at 1-27
8. Jesus Herrada (Esp) Movistar, at 1-31
9. Daniel Navarro (Esp) Cofidis, at 1-34
10. Leopold Konig (Cze) Team Sky, at 1-50