ASB Classic Tournament Director Karl Budge says having players involved in the prestigious end of year event is a real boost for the tournament.
'I think if they stay it's definitely a good choice, ' said Federer. "And, of course, I'm very, very happy and proud about it". I know this is the biggest yearly event they have here at the O2.
Anderson has won six of their eight clashes but Thiem has won the last two, which have both come this season. The Serb's 7-6 (6), 5-7, 7-6 (3) win over Federer last week at the Paris Masters was yet another reiteration of the incredibly competitive nature of their matches.
Since then Wayne Ferreira and Amanda Coetzer have reached Slam semi-finals but never a final, while Liezel Huber and Wesley Moodie have won major doubles titles.More news: Dez Bryant injury: WR suffers apparent Achilles tear at practice
More news: Norwegian frigate could sink after being rammed in harbor
More news: Red Dead Redemption 2 online beta expected to launch this month
John Isner, who has been confirmed for the 2019 ASB Classic, finished the season ranked 10th in the world and will be making his debut at the prestigious end of year event after a career best year on Tour.
Zverev, 21, has been touted about as one of the leaders of the new generation and has won three Masters titles in his short career but he has flattered to deceive at the Grand Slams.
What was to follow this year has seen Nishikori dig deep through perseverance, not giving up his childhood dream of becoming a professional tennis player and pure determination to reach the top of the game again.
Cilic, who was runner-up at the Australian Open, has qualified for the fourth time he has only one win (over Nishikori in 2016) to show so far.
However, Djokovic and every other tennis star pales in comparison when it comes to Federer's endorsements, with the 37-year-old, named the highest-paid tennis player by Forbes earlier this year for the 13th year in a row, earning $65 million from endorsements.
Nishikori returned to action in January after a five-month absence due to a right wrist injury but fell to number 39 in the ATP rankings in April, his lowest position since 2011. He has a win-loss record for 42-19 in 2018 and finished the Race to London at No 9. The battle royale will begin in London on Sunday, with Anderson and Thiem playing the opener.