The second seed was stunned 6-3, 6-0 by Claire Liu in the final of the Hong Kong Open as the American ranked 102 won her first tour title.
Eala is at a career-high 17 in the world after a breakout year in which the 21-year-old clinched her maiden title, in Washington DC, in August.
That victory made her the first player from the Philippines to win a tournament on the WTA Tour.
Eala, set to rise to 15th in the world next week, started the year ranked 50th.
"This season has changed my life; it's changed my life for the better," Eala, who finished the final with heavy strapping on her right leg, told the crowd afterwards.
Becoming emotional as she addressed her team in the stands, she said: "I'm incredibly proud of the work we've put in this year.
"We're the only ones that truly know what it took to arrive to this point in our journey.
"This is only the beginning."
Despite being the underdog, the unseeded Liu broke in the eighth game of the first set for a 5-3 lead at Victoria Park.
The American squandered the first set point but gobbled up the second to leave the large number of Eala fans in the arena stunned.
Eala, who had needed treatment for her knee in the first set, was immediately under pressure on her own serve at the start of the second set.
Liu eventually broke after an attritional opening game to grab the lead and, with that, Eala's resistance was broken.
Liu did not drop a set all week.
