Vietnamese sprint star Le Tu Chinh -- dubbed Southeast Asia's Queen of Speed -- will face a tough test in the defence of her 200m Southeast Asian Games title on Saturday after Filipina Kristina Marie Knott set a new competition record in the heats.
Both runners won their respective qualifying races in the morning session of the first full day of athletics at the 20,000 capacity stadium at the Games' main hub in New Clark City on Saturday.
Knott, 24, clocked a time of 23.07 seconds to break the SEA Games best, while the 22-year-old Vietnamese came in on 23.61.
Chinh won a sweep of sprint titles in the 2017 Games in Kuala Lumpur -- the 100m, 200m and 4 x 100m relay -- and is aiming to defend all three in the Philippines in the coming days.
Medals will also be decided on Saturday in the men's pole vault, long jump, 200m and 10,000m, and the women's hammer and triple jump. Men's and women's teams will also contest the 4 x 400m relay.
It is the last day of the swimming and diving competition at the nearby aquatics centre, where the women's 800m freestyle, 100m breaststroke and 100m butterfly will be contested, as well the men's 200m butterfly, 50m freestyle and 4 x 100m medley relay.
Elsewhere, one of the region's only gold medallists at Rio 2016 -- Vietnamese pistol shooter Hoang Xuan Vinh -- had to settle for silver on Saturday, losing out to Thailand's Kulchairattana Pongpol in the 10m air pistol contest in Subic.
About 8,750 athletes and officials are taking part in the regional Olympics spread across dozens of venues in the northern Philippines, which was hit by a deadly typhoon earlier this week.
The 11-country Games, featuring a record 56 sports, were rocked by Typhoon Kammuri which forced about half of Tuesday's events to be rescheduled.
Despite more than a dozen deaths in the storm, none of the athletes, officials or 12,000 volunteers was reported hurt and a full programme resumed on Wednesday.
The Philippines remained in firm control of the medals table on Saturday with 77 golds -- well ahead of Indonesia with 42 and Vietnam on 39.
Seven of the last 11 host nations have finished top of the medals table at the SEA Games, where the flexible sporting programme is traditionally heavily weighted towards the home team.