At least three sports fell victim to the haze yesterday, as Singapore's Pollutant Standards Index (PSI) hit an all-time high.
With air quality reaching hazardous levels, competitions in football, netball and sailing were called off over the course of the day.
"It was a good decision," said Mr Koh Mui Tee, general manager of Albirex Niigata (Singapore) Football Club, whose StarHub League Cup semi-final against Balestier Khalsa was postponed to today.
"The health of our players and fans must always be a priority."
Netball Singapore's chief executive Cyrus Medora concurred, after calling off eight Energizer National League fixtures. It was the first time in his eight years with the association that games were postponed on account of the haze.
"We decided to err on the side of caution," he said of the decision, made several hours before the scheduled tip-off time.
Mr Medora added that going forward, games will not be played should the PSI level exceed 100.
Singapore Sports Council guidelines recommend that outdoor events be cancelled when the PSI level is higher than 100.
Also adhering to that number was SingaporeSailing, which called off a regatta after just one of three scheduled races.
While health was a key factor, association general manager Jason Lim added that visibility also became a concern in the afternoon.
"The sailors couldn't see ships that were less than one nautical mile away," he said.
The hazy conditions have also cast a cloud over other sporting events this week. They include Saturday's Malaysian Super League football match between the LionsXII and Johor Darul Takzim, which has been sold out since Sunday, and the 75th Singapore Open Track and Field Championships.
It is understood that while the Football Association of Malaysia has no guidelines on the haze, it is up to match commissioners to decide if conditions are playable.
But the LionsXII's preparations for the top-of-the-table clash have already been hit, with yesterday evening's training session moved from Jalan Besar Stadium to a smaller, indoor futsal facility in Punggol. "It is not the ideal preparation for the boys," said coach V. Sundramoorthy.
Singapore Open organisers, whose event involves 288 athletes from 14 countries, including the Republic, are hoping for the best, but are prepared for the worst.
"If the haze persists at unhealthy levels, we will have a meeting with the teams that have flown in specially for the event," said Singapore Athletic Association general manager James Wong. "We will explain the situation to them before making a collective decision on whether to cancel some events like the longer distances, or even the whole meet."