Rangers suffered a shock 4-0 loss to their London rivals at Craven Cottage in the Championship.
Fulham took the lead after just two minutes when French teenager Moussa Dembele rose to nod in James Husband's left-wing cross.
Ben Pringle doubled Fulham's advantage from 18 yards in the 19th minute, and Ross McCormack slotted home from inside the box to make it 3-0 just past the half-hour mark and scrambled in a fourth on 63 minutes.
Over the course of the 90 minutes at Craven Cottage, visiting QPR had 49% of the possession, took seven shots of which two were on target, and earned two corners.
Hosts Fulham had 51% of the possession, took 13 shots of which seven were on target, and earned five corners.
Former QPR winger Sinclair was following the match, and he was disappointed with the players’ performance against Fulham.
Former Rangers forward Rodney Marsh was also following the match, and he was optimistic about the future despite the heavy loss.
In fact, Marsh has predicted on Twitter that Chris Ramsey’s side will win their next three games, which are against Bolton Wanderers (home), Birmingham City (away) and Sheffield Wednesday (home).
Don't get all the negatives from QPR fans - only out of play off spot on goal difference— Rodney Marsh (@RodneyMarsh10) September 25, 2015