The world number 18 came from a break down to take the opening set in front of a boisterous crowd largely made up of Filipino fans at the OCBC Arena.

But her Russian opponent roared back from 4-2 down to take the second set before grinding out a gruelling victory.

"You are going to have days like this, when you battle for three hours and it just doesn't go your way," said a disappointed Eala.

"I'll have to work on it but try not to make it any bigger than it needs to be."

Eala arrived in stellar form following a breakthrough season in which she beat Grand Slam winners Iga Swiatek, Naomi Osaka and Elena Rybakina.

The 21-year-old won her first WTA title at the DC Open in August and became the first Filipina to break into the World Top 20.

She had the backing of the majority of fans in Singapore, with many clad in Philippine colours and regularly voicing their support between points.

But Prozorova, ranked 165th, left them disappointed and sealed a quarter-final match against China's Wang Xinyu.

Eala now heads to Japan to compete for the Philippines in the Asian Games.

"I think I have as big a chance as any other person in the draw," she said.

"I will do my best, of course, but for now I will process tonight's loss and step on with the work."