Burnley’s unbeaten home run came crashing to an end as Reading scored two early goals and hung on for a win.
The Royals were two goals to the good after just 10 minutes to leave the Clarets with a mountain to climb.
Right-back Tendayi Darikwa grabbed his first goal for the Clarets midway through the second half to set up a grandstand finish.
But despite dominating possession the Clarets couldn’t force an equaliser to fall to their first defeat in six games.
Sean Dyche was forced to change his starting line-up that has served him so well. With Andre Gray resting a tweaked hamstring, Rouwen Hennings slotted in up front.
However, it took the visitors just five minutes to take the lead when former Blackburn striker Blackman capitalised on Michael Keane’s miskick to find the far corner with an arrowing strike.
And just four minutes later the Clarets were two goals down as the visitors shocked Turf Moor.
Some exquisite build-up play by the Royals ended with a firm ball across goal by Chris Gunter, which Piazon raced onto, and the Chelsea loanee made no mistake from 12-yards.
The Clarets finally settled and grew into the game, and on the half hour mark came close with two chances.
George Boyd’s surge down the right flank ended in a drilled cross to Michael Kightly, but the winger’s curling strike was well blocked.
Moments later the Clarets came forward once more. Ben Mee’s diagonal ball found Sam Vokes but he was crowded out before he could get his shot away.
There was an expectant roar around Turf Moor just before the hour mark, as Joey Barton made his Burnley debut.
And within moments of his introduction, Burnley were a whisker away from a way back into the game.
Boyd’s initial strike was blocked and fell perfectly for Vokes, but the Welshman was denied a certain goal by a superb block by Jonathan Obita, with the Clarets claiming a hand ball.
Finally though, the Clarets found a way past Jonathan Bond 20 minutes from time as Scott Arfield – moved out wide to accommodate Barton – crossed deep to find the advancing Darikwa, who found the back of the net from six-yards.
Four minutes later the Clarets were on the attack once more and Vokes went for goal from 25-yards, and Bond spilled his deflected drive.
Reading, who had spent the previous hour on the back foot, had a golden chance to wrap the game up five minutes from time, when Danny Williams’ cut-back was met by Blackman, but cleared off the line by Darikwa.
Two minutes later came another goal-line clearance, this time by Oliver Norwood, who denied Keane the equaliser.
And in a game of fine margins, Burnley-born midfielder Norwood rattled a 25-yard free-kick off the crossbar in the dying seconds.
Burnley: Heaton; Darikwa, Duff, Keane, Mee; Boyd, Arfield, Jones (Taylor 86), Kightly (Barton 56); Vokes, Hennings (Long 56).
Subs: Gilks, Lowton, Anderson, Ward
Yellow: Keane 52’
Reading: Bond; Gunter, Hector, McShane, Obita; McCleary (John 81), Norwood (Cooper 89), Williams, Robson-Kanu; Blackman, Piazon (Tshibola 70).
Subs: Taylor, Hurtado, Fernandez, Al-Habsi.
Attendance: 15,226 (401 away)