Ugas was only drafted in on 10 August for the Las Vegas fight to replace the injured Errol Spence Jr.
It was Pacquiao's first bout since beating Keith Thurman for the WBA welterweight title in July 2019.
"In the future, you may not see Manny Pacquiao fight in the ring," he said.
Pacquiao, 42, also told ESPN he was "thinking about retirement" and he was "60-40" in favour of quitting.
The eight-division world champion now has a has a record of 62 wins, eight defeats and two draws.
Reflecting on his defeat, he said: "That's boxing.