Japan's Kei Nishikori has vowed to bounce back from his frustrating Wimbledon exit by turning on the style during the US hardcourt season.

Nishikori blew a two sets to one lead as the 12th seed slumped to a disappointing 3-6, 6-2 6-7 (4/7), 6-1, 6-4 defeat against Italian 23rd seed Andreas Seppi in the third round on Saturday.

After reaching the last 16 at both the Australian and French Opens this year, a last-32 loss counted as a significant setback for Nishikori.

"It's not easy losing in five sets. It was a really close match," Nishikori said.

"He raised his level I think in the fourth and fifth sets. He didn't give me many unforced errors and served well, so I didn't have much chance to break him. That's the reason I lost today."

And to add to his woes, the Florida-based star struggled with a back problem for the second half of a match he seemed in control of before the injury struck.

"It was really tight, my hip and my back. It's on grass, so you have to stay low all the time," Nishikori said.

"You get tired as well. I was playing well, so it didn't affect me too much.

"I've had the injury for a few days since the first match."

The 23-year-old will now take a month off to rest and recover before focusing his attention on the North American swing, which will start for Nishikori in Washington in the lead-up to the US Open in New York in late August.

"I should be okay. I have one month after this just to train and get healthy again," he said.

"I can stay strong for the US series. I hope I can make a big impression there."

Seppi, who went the distance to beat Denis Istomin in the previous round, has now won all seven of his five-set matches in 2013 dating back to the Australian Open in January.

The 29-year-old will play former US Open champion Juan Martin del Potro or Slovenia's Grega Zemlja for a place in the quarter-finals.

Seppi, who had never been past the third round at Wimbledon in eight previous attempts, showed impressive stamina as he recovered from a slow start on Court 14.

Nishikori needed treatment on his back after breaking early in the third set and couldn't maintain his momentum despite winning the tie-break in that set.

Seppi raced away with the fourth set and Nishikori called for a medical time-out to have more treatment on his back before the decider.

The Italian kept the pressure on and landed the killer break before serving out his latest lengthy win.