Kei Nishikori says the different rules in the International Premier Tennis League (IPTL) take some getting used to.
The 25-year-old Japanese star is playing the off-season series for the first time, competing for the Japan Warriors (a team that's also in its first year.)
The league uses adjusted scoring and rules such as seven-point tiebreaks and a shot clock.
"The new rules were tough to play in especially the 20-second rule. I had to rush some of my shots," he said.
However, the world No. 8 enjoyed competing with current and retired players.
"It was a good experience for me to play with the great players like Maria Sharapova, Marat Safin and Leander Paes. I was really having fun on the court and getting support from the crowd," he said. "A lot of people showed up and it was a good tournament for me."
The league is played across five Asian cities, and features appearances by top players like Roger Federer, Rafael Nadal, Andy Murray, Serena Williams and Sharapova.