Novak Djokovic and Roger Federer win at 2015 World Tour Finals
The world number one needed just over an hour to see off eighth seed Nishikori, and ended the afternoon with a trophy in his hands as he was confirmed as the 2015 world number one.
Djokovic, 28, won the Australian Open, Wimbledon and US Open, and went within one match of the calendar Grand Slam, losing to Stan Wawrinka in the French Open final.
“Undoubtedly it has been the best season and the best year of my life – I became a father and I got married. Those are the kind of trophies and milestones that mean the most to me,” he said.
Djokovic might be the dominant force right now but Federer holds a record six end-of-season titles and remains the fans’ favourite.
A large number of travelling Swiss swelled the capacity evening crowd as their man found his form to rack up his 49th win in 60 matches and 14 trips to the season finale.
Federer started surprisingly poorly, double-faulting twice as he dropped serve to love in game three, only for Berdych to return the favour in the next game, almost tripping over when a drop shot caught him out.
The Czech, 30, was struggling to find any rhythm and eventually paid for a first-serve percentage of just 41% as three errors handed over the key break at 4-4.
Federer took complete control with seven games in a row for a 4-0 lead in the second set and promptly wrapped up victory.
The Swiss will take on world number one Djokovic in the second round of Stan Smith Group matches on Tuesday.