Victorious in all of the bunch sprints in this year's race, the Argos-Shimano fastman used his trademark last-ditch acceleration to fend off Italian Elia Viviani by half a wheel on a motor racing-circuit finish to stage seven.

Allan Davis of Australia was third while Katusha rider Joaquim Rodriguez of Spain retained the overall lead.

"After taking that first win everything has been a bonus and it becomes easier to suffer," Degenkolb told reporters.

"Today we suffered, you can see that from when we were in one line close to the finish because we were going so fast. Team Sky did a great job working for their sprinter Ben Swift and I even had a few problems following them.

"But my guys had good timing, dropped me off exactly where I needed to be, and I came up to the line just in time for the win."

Degenkolb said his third victory justified the Vuelta organization's decision to invite his team for the second year running.

"We deserve our place here and we deserve our place in the Tour de France again next year too," he added.

"Normally the points jersey here is won by one of the overall classification riders, not like in the Tour (de France), but I'll fight for it. I fight for everything."

Rodriguez stayed in front for the fourth day. Britain's Chris Froome occupies second spot, 10 seconds back, while Spain's Alberto Contador is third at 36 seconds.

In the closing kilometer Froome attempted to guide Sky team mate Swift into a good position but he said later they mishandled the finish.

"We worked really hard for him but then left him to go for it too far from the line, it was a mistake," said Froome.

Sky rider Rigoberto Uran of Colombia, who started the day in fourth position overall, was dropped when the bunch split close to the finish.

The Olympic road race silver medalist lost more than a minute and slid out of the top 10.

After munching half a plate of rice and fried tomato he took into his news conference, Rodriguez said the seventh day of soaring temperatures had been difficult to handle.

"This heat ends up being unbearable, every time you go back to the team car during a stage and feel the air conditioning coming out of the window you feel very envious," he added.

"It was a very nervous stage throughout, lots of splits in the peloton, you could sense the tension."

The three-week 2012 Vuelta a Espana ends in Madrid on September 9.

Watch video highlights from all stages of this year's vuelta in our videos section (U.S. access only).