Almeida was unable to keep pace with GC rivals Carapaz (Ineos Grenadiers), Jai Hindley (Bora-Hansgrohe) and Mikel Landa (Bahrain Victorious) for the second successive stage in the mountains, particularly as the day's final ascent approached.
The UAE Team Emirates rider was thought to have been preserving his energy for the 8-kilometre plateau from the summit to the finish in Lavarone, though his deficit only increased.
Carapaz, Hindley and Landa worked together to distance their Portuguese rival, who reached the finish line 1'04" down on the group and 1'54" adrift of its pink-laden leader.
Such a setback has all but ruled out overall victory for the 23-year-old, but he remains hopeful of a place on the podium, pending the remaining four stages.
"To be honest, I didn't lose that much time on the climb," Almeida said in the mixed zone.
"It was more on the flat afterwards. I was alone and against three guys, it's hard.
"But I still managed to limit the losses, so it wasn't a bad day."
"I mean, everything is possible, but I would say it's almost impossible to take pink," he added.
"But I think the podium is still possible. I still believe."
With Carapaz three seconds ahead of Hindley, Almeida now sits fourth overall behind Landa, who holds a 49-second lead heading into Stage 18.
The 17-kilometre time trial set to conclude the Giro looms as Almeida's best chance to cement his place on the podium, but he will first have to navigate runs into Treviso, Slovenia and the Dolomites.
"There are more hard stages to come but I'm still confident I can do well," Almeida said.
"Give everything I have and see on the finish line."
The Giro d’Italia continues tonight on SBS with a flat stage to Treviso for Stage 18. Watch from 9:30pm (AEST) via SBS On Demand with television coverage beginning at 11pm (AEST) on SBS. WA viewers can watch from 9pm (AWST) on SBS VICELAND.
