And to make matters worse for the beleaguered hosts Alasdair Dickinson, making his return from a foot problem, was forced off the field after 49 minutes on a stretcher.
There had been hopes in some quarters that the 33-year-old loosehead prop would come through this one and be available for a Scotland return against England next week, but that will not happen now.
The home side went into this one having lost all four matches in the PRO12 during February and having not tasted victory in the league since the last day of 2016 at Zebre.
Five minutes before kick-off the rain started to fall heavily but Edinburgh got off to a purposeful start.
They had a lot of early possession, but did not do too much with it and the 10th minute came and went with no score on the board.
Edinburgh’s pack was going well though and in the 15th minute they won a penalty when the Ospreys collapsed the scrum under pressure. It was some 30 metres out and stand-off Duncan Weir kicked it over to put Edinburgh 3-0 up.
However, as has been the tale for much of Edinburgh’s campaign, they conceded points soon after scoring. Three minutes later the home side gave away a penalty after a high tackle and Ospreys stand-off Sam Davies kicked it over.
And in the 22nd minute the Welsh side went into the lead when a bit of Davies magic saw them score a try. The stand-off ghosted through a gap in the defence and then gave a lovely inside pass for centre Josh Matavesi to go in under the posts from 20 metres out. Davies converted and Edinburgh were 10-3 behind with the rain showing no sign of stopping.
The Welsh side, chasing an end of season play-off spot, took heart from those scores and in the next 10 minutes had all the possession. Edinburgh needed something to kick start their evening and get the crowd going and in the 33rd minute they did hack a ball forward into the visiting ‘22’ and back-row Jamie Ritchie put in a thumping tackle on Ospreys full-back Dan Evans. It did not come to anything, but it showed Edinburgh were up for the fight.
They were dealt a blow in the 37th minute when second-row Ben Toolis was forced off injured. He was replaced by Anton Bresler who was making his first appearance of the campaign after a long injury lay-off.
Before the break Edinburgh had a great chance to get a try on the board. The ball was spun right and winger Damien Hoyland went close, but a few phases later the ball was lost forward to leave it 10-3 to the Ospreys at half-time.
At the start of the second half Toolis was back on for Edinburgh after he passed a head injury assessment. And the home team looked up for the challenge, Weir having a good early run.
A few minutes later they won a penalty from a lineout. It would have been kickable, but they went for touch and earned a lineout. Toolis took it well and they drove towards the line, but in the move Dickinson went down and had to be helped off the field injured. It looked like a recurrence of the recent foot injury – to be confirmed – and he was replaced by Derrick Appiah.
Five minutes later back-row Magnus Bradbury then limped off to add to Edinburgh’s woes.
The good thing from their point of view was that despite the injuries they were still in the game and in the 62nd minute Weir kicked a long range penalty and they were just 10-6 behind.
The game then became a ‘kicking fest’ for five minutes before Edinburgh conceded a lineout penalty. Davies took his time, but from some 35 metres out he kicked it over to restore the Welsh side’s advantage.
Weir then kicked a third penalty to make it 13-9, but in the final seven minutes Edinburgh could not score again as they slumped to a loss.
Scorers: Edinburgh Rugby: Pens: Weir 3. Ospreys: Try: Matavesi. Pens: Davies 2. Con: Davies.
Edinburgh Rugby: Blair Kinghorn; Damien Hoyland, Glenn Bryce, Chris Dean, Rory Scholes; Duncan Weir, Sam Hidalgo-Clyne, Alasdair Dickinson, Neil Cochrane (C), Murray McCallum, Grant Gilchrist, Ben Toolis, Magnus Bradbury, Jamie Ritchie, Cornell Du Preez. Subs: Stuart McInally, Derrick Appiah, Kevin Bryce, Anton Bresler, Lewis Carmichael, Nathan Fowles, Michael Allen, Junior Rasolea.
Ospreys: Dan Evans; Keelan Giles, Kieron Fonotia, Josh Matavesi, Dafydd Howells; Sam Davies, Tom Habberfield; Nicky Smith, Sam Parry, Brian Mujati, Tyler Ardron, Rory Thornton, Olly Cracknell, Sam Underhill, James King. Subs: Hugh Gustafson, Paul James, Rhodri Jones, Joe Bearman, Dan Baker, Brendon Leonard, Jonathan Spratt, Jay Baker.
Referee: George Clancy (Ireland).