The ATP World Tour Finals could stay in London when the deal ends in 2020.
The end-of-season showdown between the best players in the men’s game was brought to the capital by ATP CEO Chris Kermode in 2009.
“As the head of the Tour, I have the responsibility to ask, ‘Is this the right place to have it?’” Kermode told Standard Sport.
“It would be very difficult to find a city that could get two sessions a day of 17,500 people.
“But we need to keep looking, not rest on our laurels and evaluate in 2020, so who knows.”
ATP World Tour Finals 2017 - In pictures
In the bidding process last time, London vied with other European cities - with Berlin and Paris potential challengers after 2020 - while there was also interest from cities in Asia, the Middle East and South America.
Kermode added: “We’ll have to weigh up what we’ve created here and it’s got real roots now in London.
“But it doesn’t necessarily mean it can’t happen somewhere else.”
Roughly quarter of a million people attend the finals at the O2 Arena each year, with Roger Federer the favourite to win the title for a record seventh time on Sunday after topping his group with a third straight win on Thursday.
