Djokovic clinches year-end No. 1 ranking

London, England ( - For the third time in four years Novak Djokovic will finish as the No. 1 player in the world.

The top-seeded Serbian star blitzed sixth-seeded Tomas Berdych 6-2, 6-2 in 69 minutes in Friday's round-robin action at the season-ending ATP World Tour Finals to secure his top-ranked status.

The 27-year-old Djokovic also secured a berth in Saturday's semifinals at the Tour Finals after capturing his round-robin group with a perfect 3-0 record this week.

Djokovic is the seventh player to finish as a year-end No. 1 on three occasions, joining Pete Sampras (6), Jimmy Connors and Roger Federer (5), Ivan Lendl and John McEnroe (4), and Rafael Nadal (3).

"It's an incredible achievement. Being No. 1 in the world is one of the biggest challenges a tennis player can have," said Djokovic.

"I've been playing since I was four. I was very fortunate to have very knowledgeable people, people who believed in me, and believed in my talent."

The seven-time Grand Slam champion is also only the fourth player -- after Lendl, Federer and Nadal (twice) -- to hold, lose and regain the year-end No. 1 ranking. This is the 11th straight season that the year-end No. 1 ranking has been held by Djokovic (2011-12, '14), Federer (2004-07, '09) or Nadal (2008, '10, '13).

The two-time reigning and three-time overall Tour Finals champ Djokovic beat Nadal in last year's final here in London and the super Serb has won his last 30 indoor matches.

Djokovic spearheaded Group A, which also featured third-seeded Australian Open champion Stan Wawrinka (2-1), Berdych (1-2) and eighth-seeded U.S. Open champ Marin Cilic (0-3).

The Wimbledon champ Djokovic will face U.S. Open runner-up Kei Nishikori in Saturday's first semifinal. Nishikori stunned Djokovic in a semifinal at the U.S. Open in September. The two men have split four career matchups, including two meetings in 2014. The Serb beat the nifty Japanese at the Paris Masters just two weeks ago.

Saturday's other semifinal will pit the second-seeded former world No. 1 Federer against his Swiss Davis Cup teammate Wawrinka, who reached the final four here by winning three games against Cilic in the final round-robin match of the week Friday night at The O2. Wawrinka closed out the round-robin stage with a 6-3, 4-6, 6-3 victory over Cilic.

This week's top-four seeds all made it through to the round of four.

The two semifinalists from Group B were established on Thursday, when the Tour Finals king Federer (3-0) and the fourth-seeded Nishikori marched on in London. The other players from that group were fifth-seeded Andy Murray (1-2) and seventh-seeded Milos Raonic (0-2), who was replaced by first-alternate David Ferrer (0-1) on Thursday. Ferrer was forced into action on Day 5 when the Canadian slugger Raonic withdrew from the exclusive eight-player event due to a quad injury.

The 17-time Grand Slam titlist Federer holds the record for the most titles at this prestigious season-ending tournament with six.

Federer will meet his good friend Wawrinka for a 17th time on the ATP circuit seeking a commanding 15th victory. They've split a pair of matchups this season, as Wawrinka prevailed in a final at the Monte Carlo Masters and Federer came out on top in a quarterfinal at Wimbledon.