It's anyone's guess who's going to win the 2015 Vuelta a España as race hits final week

The Vuelta a España is moving closer to its finish in Madrid, but it is anyone's guess who will win the race overall.

The tall and skinny Italian, Fabio Aru (Astana) holds on to the red leader's jersey, but only just. Spaniard Joaquím Rodríguez (Katusha), winner on two days in the Tour de France in July, won today's summit finish at Sotres and moved within one second of the lead.

Time trial specialist, Dutchman Tom Dumoulin (Giant-Alpecin) lost ground - 51 seconds - but still hovers at 1-25 minutes behind Aru.

Others have a chance, too. Pole Rafal Majka (Tinkoff-Saxo) sits third overall at 1-24 and Colombian Esteban Chaves (Orica-GreenEdge) fifth at 1-34.

"The Vuelta is all knotted up, the race overall will be a game of seconds," Rodríguez explained at the finish, at 1230 metres in northern Spain's Asturias.

"Tomorrow there will be another shakeup on the stage. Definitely, though, after the Burgos time trial, we will have a clearer picture of the situation."

Tomorrow's stage could be the toughest of the 2015 Vuelta, or at least runner up to the Andorra stage last week. To reach the Alto Ermita de Alba summit, the riders must climb 5010 metres over 185 kilometres.

They have a rest day on Tuesday, but the next day, the Vuelta scheduled a 38.7-kilometre time trial that could swing the race back in Dumoulin's favour.

The tall 70-kilo Dutchman lost time today. He is expected to lose more tomorrow, but could come close or take over the race lead Wednesday in the time trial.

Dumoulin rode to a bronze medal in the world championships time trial last year in Ponferrada, Spain, behind winner Bradley Wiggins and Tony Martin. Aru and Rodríguez both suffer when put on aero time trial bikes and asked to ride long distances.

In 2012, Rodríguez lost the Giro d’Italia overall to Canadian Ryder Hesjedal on the last day in a time trial through Milan.

Aru, who barely held on to the Vuelta's red jersey today, did not appear happy with the situation in the press tent at the summit.

"Both Dumoulin and Rodríguez are dangerous for me," Aru explained.

"It can't be positive with today's result. I lost time to 'Purito' [Rodríguez], 25 seconds. For sure, I'm not happy with that.

"Tomorrow is very very hard. Then there's the time trial... What [Dumoulin has] shown in the time trials already is that he can gain. The question is how much. I don't know. I don't know."