SINGAPORE - Organisers of the International Premier Tennis League (IPTL), in town for the second of three legs this season, are expected to offer upgrades and refunds for fans who bought tickets but will not see some marquee players after last-minute changes.

In a tweet on Tuesday afternoon, the IPTL apologised for the late turn of events and said it would be giving out information about upgrades and refunds soon.

It was made known earlier in the day that former world No. 1 Roger Federer will also not be featuring this season, which followed news on Monday that another big name, Serena Williams, would also not appear here.

Organisers had promoted both stars as headline acts for the Hyderabad and Singapore legs respectively.

Their absence leaves the IPTL, now into its third season, shorn of the star power the event had in its first two years when the likes of Federer, Rafael Nadal, Andy Murray, Maria Sharapova and Williams took part.

IPTL founder and Indian doubles player Mahesh Bhupathi told The Straits Times on Monday when he explained Williams' absence: "We were trying to get it done and we've had some challenges financially.

"It's been rough. We've got some good tennis and we hope the format is something that will pull in the fans."

But the late announcement of the players' absence - with the player list made known less than a fortnight before it began - will not sit well with fans who had purchased tickets in the hope of seeing the sport's biggest names in action.

The Singapore leg of the IPTL opens on Tuesday night at the Singapore Indoor Stadium and takes place until Thursday before it moves to Hyderabad.