Samoa won 27-15 at Apia Park on Saturday after Tonga had two players sinbinned.
But Tonga midfielder Cooper Vuna has criticised the conditions, saying no top tier nation would be expected to play on a pitch which degenerated into a muddy morass following torrential rain.
"Please @WorldRugby enlighten us all on what processes you took to allow this game to go ahead," Vuna said on Twitter.
"My question is – if a tier 1 team was to play that day ,would the game still go on?
Tonga's Hurricanes lock Sam Lousi also tweeted his displeasure.