LONDON -- It was another easy win for Novak Djokovic, but certainly one that he will remember.
The Serb's celebrations at the O2 Arena after Tomas Berdych sent a final shot wide on Friday spoke volumes. Djokovic raised his arms above his head and gave a roar of joy, a large grin across his face. His comfortable 6-2, 6-2, win over Berdych had just sealed another year-end No. 1 ranking and a semifinals berth in the ATP Finals.
"Being No. 1 of the world is the pinnacle of the sport," said the 27-year-old Djokovic.
"One of the highest and most difficult challenges is to be No. 1 nowadays, especially because the tennis has become very competitive in the last five, ten years, very physical. To have a shot at No. 1 of the world, you need to be consistently healthy and successful throughout the year."
Berdych dropped his first two service games as the Serb took control from the baseline. Djokovic again broke twice in the second set with a range of forehand winners, powerful returns and net charges that frequently left Berdych stranded.
Djokovic, the Wimbledon champion, will finish the season No. 1 for the third time in four years. He's the seventh man to accomplish the feat at least three times.
"I believe everything happens for a reason. So I'm here for a reason, and I managed to finish the year as No. 1 for a reason," he said.
Djokovic and Federer have swept their groups in London, and are on course to meet in Sunday's final. After enduring one of his worst seasons last year, Federer is back to his best and proved to be a worthy challenger in their battle for supremacy.
"Roger is playing some of his best tennis since I know him and since I watch him," said Djokovic. "We played an amazing final of Wimbledon. We fought all the way through basically the last few days of the season for No. 1. That proves how good he played over the course of 12 months. "
Before a mouth-watering potential showdown, Djokovic will first take on Kei Nishikori in the semifinals, while Federer will face his Davis Cup teammate Wawrinka or US Open champion Cilic, who were meeting later Friday.
Djokovic has been in supreme form since the birth of his first child, Stefan, on Oct. 21, and has won 16 of his last 17 matches. In London, he extended his two-year-old indoor winning streak to 30 matches and has lost only nine games this week.
"I think I had a great season and a great year overall for my private life and professional, as well," he said. "Considering all the things that have happened and circumstances, I thought I have done very well."
Besides winning his seventh Grand Slam title at the All England Club, Djokovic was also runner-up at the French Open, and won six titles.
Before taking some time off, he now has two more matches to win to claim a fourth title at the Finals and become the first player since Ivan Lendl from 1985-87 to win the elite tournament three years in a row.