In the marquee scheduled matchup of the day, a third-seeded Federer handled seventh-seeded fellow former No. 1 Andy Roddick 6-3, 6-2 in just 64 minutes. Federer did not allow even one break-point chance for the overmatched Roddick on Day 5.
Federer is now a lopsided 21-2 lifetime against Roddick, including a 4-0 record here in his hometown of Basel. The Swiss icon also topped Roddick here last year in the semifinals.
The 30-year-old Federer has won four of the last five titles in Basel, including a victory over Djokovic in last year's finale.
Federer's semifinal opponent on Saturday will be his good friend and fellow Swiss Stanislas Wawrinka. Federer is 9-1 all-time versus Wawrinka, including a 3-0 mark this year.
The reigning U.S. Open, Wimbledon and Australian Open champion Djokovic came from behind to beat 2005 Basel runner-up Marcos Baghdatis 2-6, 6-2, 6-3 at St. Jakobshalle. The 2009 Basel champion Djokovic converted all three of his break-point opportunities for the victory, which took 1 hour,39 minutes.
Djokovic is now 6-0 lifetime against Baghdatis, which includes a third-round victory at the All England Club this past summer.
The Serbian star is now an amazing 67-3 for the year.
The high-flying Djokovic returned to action this week after being sidelined with a back injury since mid-September. He was last year's Basel runner-up to the hometown hero Federer and upset Federer in the final here two years ago.
"I started slowly, no life on the court, and he (Baghdatis) took his chances," Djokovic said. "My body is still getting used to this competition mode. I have to stay patient."
"It's a great feeling to reach three semifinals in six weeks," Nishikori said.
Switzerland's second-best player, the 19th-ranked Wawrinka, secured a final-four berth by blasting German Florian Mayer 6-2, 6-2 in 64 minutes.
The 2011 Basel champion will collect $450,000.