QPR boss Steve McClaren admitted a second-half gamble against Hull backfired.
Rangers were beaten 3-2 at Loftus Road, where Jarrod Bowen scored twice for the Tigers.
With his team 2-1 down and looking fragile at the back, McClaren took a risk by bringing on striker Tomer Hemed in place of midfielder Geoff Cameron.
Six minutes later, Hull carved QPR open and Bowen netted their all-important third goal.
Luke Freeman scored in stoppage time but Rangers were unable to avoid only their second defeat in Championship matches.
Goals from Bowen and Markus Henriksen had put Hull two up before Pawel Wszolek pulled a goal back for Rangers, who went close to equalising when Angel Rangel volleyed against the post shortly before the interval.
A second-half onslaught looked likely but did not materialise, prompting McClaren to make the risky substitution just after the hour mark.
“When you gamble – and we had to gamble – you can be on the wrong end of it,” said McClaren.
“I still felt at half-time that we’d win, but we were always susceptible to that third goal. That’s what happens when you throw caution to the wind, which we had to do. It didn’t pay off today.”
Rangers recently kept four clean sheets during a five-match unbeaten run but have shipped a total of nine goals in their past four matches.
McClaren said: “That was our second defeat in 10 games. Over that 10-game spell we’ve been very good defensively and have kept clean sheets.
“Now we’re not keeping clean sheets and we need to get back to that. We dust ourselves down and go again.
“We’ve kind of fallen off the wave and we need to get back on another wave. We’ve got to get back to working hard and doing the basics right.
“We need to get back to the basics, get back on the training ground, and get the simple things right, because we certainly look like we can score goals.”