World number five Ferrer was beaten 6-3 6-4 by Serb Troicki in the hard-court event, a defeat which dealt a blow to the Spaniard's bid to qualify for the ATP World Tour Finals in November.
Novak Djokovic, Roger Federer and Rafael Nadal have already confirmed three of the eight spots and Ferrer finds himself seventh in the battle to qualify.
It took Troicki, ranked 174 in the world, just 66 minutes to cruise past the 32-year-old and he racked up 13 aces in a shock victory.
The two players were neck-and-neck for the first five games in the opening set, until Troicki stole the initiative by breaking Ferrer to love to go 4-2 up and saw out the set to take the upper hand.
Ferrer then found himself a break down after losing the first game of the second set as Troicki rose to the occasion.
The underdog saw a couple of match points go begging in the final game, but he finally sealed only his fourth win from 51 attempts against top-10 opposition and was delighted to claim a big scalp.
"David is a great fighter, a great player," Troicki said.
"He always gives his best. It's amazing to beat him because I've never had a chance before.
"This was maybe a better surface for me, but it's great to beat him. It's special for me."
Murray boosted his slender chances of reaching the World Tour Finals in London by easily dispatching Somdev Devvarman 6-3 6-3.
The British number one cruised in the first set, winning in just 36 minutes as he twice broke the 141st-ranked Indian.
The second set was not quite so straightforward for Murray, as he immediately gave Devvarman a lifeline by losing his own serve after breaking the 29-year-old in the second game.
However, the 2013 Wimbeldon champion bounced back to break Devvarman again in the sixth game and eased to victory as he battles Ferrer, Milos Raonic and Grigor Dimitrov for a spot in the World Tour Finals.
Murray's next opponent will be Lukas Lacko after the Slovakian fought past Ricardas Birankis of Lithuania 6-4 7-6 [7-1], while sixth-seed Santiago Giraldo confirmed his place against Troicki in the quarter-finals with a 6-4 6-3 triumph over Australian qualifier Thanasi Kokkinakis.