Despite Gloucester's resilience this season, the game had slowly slipped away in a second half, played in terrible weather conditions, which was riddled with penalties conceded and handling errors.
It was a frustrating second 40 minutes for Gloucester who had looked good value for their first half lead until Ospreys fly half Matthew Morgan kicked his team back into contention.
The home team definitely played the conditions better in the second half, while Gloucester were hit by the loss of fly half Billy Burns, leaving the team without a recognised fly half on the pitch.
Although the Ospreys didn't really threaten the Gloucester line until late on, their goal kicking was spot on and they were given plenty of opportunity to kick their goals.
Tom Grabham's 67th minute try, which opened up a 26-13 lead, looked to be the final nail in the coffin but, against all the odds, Gloucester launched an astonishing late comeback.
Dan Murphy pounced from close range before a powerful driving maul resulted in a penalty try. Dan Robson converted both and Gloucester had crept into a 27-26 lead as the game went into injury time.
If ever a good exit was required, it was now. However, Gloucester couldn't secure their own lineout ball and Ospreys had possession.
A half break followed before number eight Morgan Allen drove over from a couple of metres out to secure the win and leave Gloucester with the bitter taste of defeat in their mouths. Having battled their way back, it was a cruel blow.
Defeat isn't necessarily the end of the LV= Cup dream. Two seasons ago, Gloucester lost at the Dragons on a similarly foul night and went on to win the trophy.
However, they must bounce back against London Welsh next weekend.
Gloucester were forced into a late reshuffle following the withdrawal of fly half Tim Taylor. Billy Burns stepped up off the bench and took over the number ten shirt.
After an impeccably observed minute's silence, play got underway with rain teeming down at the Liberty Stadium and an open handling game looking doubtful.
Some early Gloucester indiscipline gave the Ospreys the first chance of points, but Matthew Morgan dragged his penalty attempt wide left.
Gloucester responded with some muscular ball carrying from the likes of Tim Molenaar and Ross Moriarty but overambitious offloading halted the momentum.
However, Gloucester had field position and more robust work from the forwards led to a penalty chance and Billy Burns made it 3-0 after nine minutes, only for Morgan to reply in kind two minutes later.
Some scrappy play followed until the Gloucester scrum forced the Ospreys eight to buckle, Yann Thomas having his opposite number in real trouble, and Burns nudged his side back in front after 17 minutes.
The home side hit back with some one out rugby, working their way gradually into the Gloucester 22, and Matthew Morgan dropped a neat goal to level the scores.
Gloucester duly went back to their pack and the Ospreys had no answer, conceding penalty after penalty and, eventually, second row James King was yellow carded.
The kick went to the corner, Tommaso d'Apice almost drove to the line but offloaded neatly for Yann Thomas to power over. Burns converted amidst a cacophony of boos.
A good exit was needed off the restart, but Gloucester's Achilles heel this season resurfaced and Morgan was able to drop another goal to keep his side in it at 9-13 after 30 minutes.
And it was Morgan who narrowed the gap to 12-13 a couple of minutes later as Gloucester fell off a couple of tackles before conceding a penalty which was gratefully received and kicked.
Gloucester's indiscipline was threatening to cost them dear at this point, as the Ospreys were being gifted cheap possession and territory without really looking particularly potent with ball in hand. Creating kicking opportunities for Morgan seemed to be the main tactic.
But it worked again for the home side on 42 minutes, as a well executed catch and drive was halted illegally and Morgan slotted the penalty to give his team the half time lead.
Gloucester would have gone into the break scratching their heads and wondering how they trailed at half time.
However, they hadn't executed well enough when in possession and leaked enough penalties to allow the Ospreys back into the game.
This game was more than winnable but Gloucester would have to earn the victory with an improved second half performance and in worsening weather conditions.
It was almost first blow to the Ospreys, but Morgan was off target with a penalty after referee David Rose penalised Gloucester for an offence even the home crowd seemed puzzled about!
The rain was really hammering down and handling becoming more and more difficult. The Ospreys one out tactic was proving increasingly effective in the conditions.
Also hurting the Cherry and Whites was a lack of line speed in defence and difficulty handling the high ball.
It was all conspiring to put Gloucester under real pressure and it was becoming difficult to see where the spark of inspiration was going to come from, particularly when Peter Buxton was sinbinned and Morgan's penalty extended the lead to 18-13 after 59 minutes.
Frustration was really growing in the Gloucester ranks, typified when referee Rose made a poor call as he deemed Shane Monahan offside chasing a kick ahead.
Replacement Sam Davies rubbed salt in the wound by promptly extending the lead to 21-13 with another well struck penalty.
More indiscipline promptly forced Gloucester on to the back foot again and, sadly, it came as no surprise when more pressure created numbers on the left and wing Tom Grabham slid over in the corner.
Dan Murphy drove through a close range ruck five minutes from time to give Gloucester a glimmer of hope as Dan Robson's conversion made it 26-20, and there was suddenly a spring in the stride.
However, just as the Gloucester supporters, who had made the trek west to follow their team, started to celebrate this unexpected turn in fortunes, there was one last twist in the tale and their cheers died on the wind.
|Ospreys Score Card|
|Gloucester Rugby Score Card|