The Clarets saw their unbeaten league record ended as Forest won the battle of the top two to knock Burnley off the summit of the Professional Development League’s northern group.
With the Clarets undefeated in 17 league games and Forest unbeaten in 11, something looked likely to give.
And it was the visitors who cracked to surrender top spot on goal difference.
With captain Anthony Glennon becoming the sixth member of the Clarets’ squad to earn a loan move in pursuit of first-team experience, coach Andy Farrell’s hand was weakened in favour of the bigger picture.
But this was still a low-key performance from the Clarets, who conceded goals either side of the break and then never really looked like completing a possible comeback triggered by Josh Benson’s penalty.
Due in large part to the changes in personnel, just three of the side that kicked off the Clarets’ final game of 2019 were in the starting line-up at the City Ground.
And following the Christmas break Burnley were slow to get going.
Bobby Thomas headed an early chance over the top after Jimmy Dunne had flicked on a long throw from Jordan Cropper.
And Rob Harker had two sights of goal, volleying into the midriff of Marios Siampanis before failing to beat the Forest keeper from a much more presentable opportunity after Josh Benson’s persistence had forced an opening.
The first goal looked criticial and having failed to grab it and take control before the break, the Clarets fell behind six minutes before half-time.
Kieran Hayes had earlier hit the foot of a post with an angled shot and from the penalty spot he made no mistake in slotting home after Liam Sole had been upended in the box.
The Clarets looked to hit back with a more positive start to the second half but struggled to find a way through Forest’s back line and with 63 minutes gone found themselves 2-0 down.
Forest hadn’t posed much of a threat but were always lively on the break and when Yassine En-Neyah got away down the right-hand side, his low cross was clinically fired into the top corner by Keith Asare.
The Clarets’ unbeaten record was hanging by a thread but just four minutes later they were handed a route back into the game through a penalty of their own.
Asare pulled back Burnley’s trialist winger and Benson kept his composure to send Siampanis – whose late penalty save at Turf Moor in September had denied the Clarets a win in the reverse fixture – the wrong way to halve the deficit.
The Clarets then pushed to rescue a point but didn’t do enough to force an equaliser, Dunne seeing an effort at full stretch grabbed under the bar by Siampanis and the trialist seeing the last chance come and go in a crowded penalty area in stoppage time as Burnley finally tasted defeat.
Nottingham Forest: Siampanis; Lawrence-Gabriel, Stewart, Barnes, Gallacher; Sole (Walsh 78), Fornah, Edser, Asare; Hayes (Swan 88), En-Neyah. Substitutes: Statham, Rama, Hammond.
Burnley: Jensen; Cropper, Thomas, Dunne, Koiki; Trialist, Benson, Goodridge, Tucker; Harker, Mumbongo (McGlynn 64). Substitutes: McMahon, Younger, Woods, Conn-Clarke.
Referee: Richard Eley