Nikolay Davydenko reacts after defeating Robin Soderling during their ATP World Tour Finals match against in London on Friday. (Sang Tan/Associated Press)

Nikolay Davydenko grabbed the last semifinal spot at the ATP World Tour Finals by beating Robin Soderling 7-6 (4), 4-6, 6-3 Friday, knocking defending champion Novak Djokovic out of the tournament.

Davydenko, Djokovic and Soderling all finished with two wins in the round-robin phase, but the third-ranked Serb was eliminated on sets. Soderling had already secured advancement and finished at the top of Group B.

Davydenko broke Soderling for the first time to take a 4-2 lead in the decider and converted his second match point when the Swede missed an easy forehand at the net.

Djokovic beat Rafael Nadal 7-6 (5), 6-3 earlier Friday, handing the Spaniard his third straight loss at the tournament.

Rafa on losing skid

Nadal is on a four-match losing streak after losing to Djokovic in this month's Paris Masters semifinals. If Djokovic advances, he can overtake Nadal for the No. 2 ranking by winning the tournament.

Nadal finished with nearly three times as many unforced errors as winners — 35 to 12. He needed treatment on his lower back at 2-1 in the second set and had his serve broken in the next game.

The Spaniard broke back twice in the first set to reach the tiebreaker, but then he shanked a couple of forehands and fell behind 6-2. He saved three set points before sending a forehand wide on the fourth.

Nadal said he lacked the "necessary calm" at decisive moments.

"For example, the forehand in 6-5 of the tiebreak was an easy ball," he said. "And when you are playing good, that wouldn't be a problem, that ball. But, you know, I had the mistake, I lose the set, and with that set the match."

Nadal showed flashes of his speed, chasing down a number of Djokovic's drop shots at the net. But his efforts were usually in vain, as most of his returns merely resulted in easy volley winners for the Serb.

Nadal's season has been interrupted by injuries. He is 1-9 against top-10 opponents since losing to top-ranked Federer in the Madrid Masters final in May.