The U23s lost out in a competitive run-out against Lancaster City as they near the start of the Professional Development League season.
Connah’s Quay Nomad’s run in the Europa League meant the Welshmen had to pull out of the scheduled fixture.
But with Lancaster stepping in to fill the void, it meants another beneficial 90 minutes for Steve Stone’s side before they kick off their league campaign at Millwall next Friday.
Most of Stone’s available squad was given some game-time at Barnfield, including midfielder Adam Phillips after he signed a deal to join the Clarets on Friday.
But after dominating the first half, Burnley ended up second best as the Dolly Blues scored three times after the break.
The Clarets had chances before half time to take the lead, 16-year-old Lewis Richardson going closest as his quick feet in the penalty area made space for a shot which was saved by Sam Ashton.
But a number of changes at the break saw the Clarets lose their grip on the game as Lancaster – whose assistant manager Graham Lancashire was back at the club he served as a striker in the 1990s – went ahead through Paul Dawson’s low strike with an hour gone.
Burnley had chances to level as substitutes Will Harris and Tunde Bayode threatened.
Harris saw a header superbly saved by Ashton before Bayode screwed a shot wide on his return from injury.
And Lancaster, who start their BetVictor Premier Division push in a fortnight’s time, then took full advantage of those let-offs with two late goals.
A trialist doubled the visitors' lead before on-loan Preston defender Jack Armer lashed in a fierce strike in the last minute after the Clarets failed to deal with a long throw as they left themselves with work to do in their final week of pre-season.
Burnley: Trialist, Senior (Cropper HT), Thomas (Wilson HT), Younger, Koiki; Trialist, Phillips (Trialist HT), N’Guessan, Conn-Clarke (Bayode HT); Richardson, Harker (Harris HT).
Lancaster (starting): Ashton, Fensome, Armer, Wills, Hudson, Steel, Trialist, Norris, C Bailey, Trialist, Dawson.