SINGAPORE (AP) — Even though Novak Djokovic and Roger Federer have yet to play in the new International Premier Tennis League, founder Mahesh Bhupathi says it has already made its presence felt and will be expanded next year.

"We've achieved something out of the box here that's very challenging," Bhupathi said on Thursday, a week after the fast-paced, mixed-team format made its debut in Manila.

It features past and present players such as Andre Agassi, Serena Williams, Maria Sharapova and Ana Ivanovic in four teams in four countries in Asia and the Middle East.

"We're definitely going to add two cities next year," Bhupathi, the retired doubles specialist, said. "We have had a lot of interest now, we had four cities ready to sign on the dotted line by the end of next month.

"The franchises are the ones picking the teams, so a lot depends on how much they're going to spend (to get top players)."

The IPTL, inspired by cricket's successful Indian Premier League, is being played over four legs. Results are decided by aggregating games won from five matches — men's and women's singles, men's doubles, mixed doubles, and legends singles.

The one-set matches include innovations such as "power points," which give players a chance to double up on a point, time-outs, and doing away with lets and advantage points.

From Manila, it moved to Singapore, and the remaining two legs will be in New Delhi this weekend, then Dubai next week.