Leicester Tigers kept their Heineken Cup hopes alive with a hard-fought 15-15 draw at the Liberty Stadium - but the result knocked the Ospreys out and with them went the last hope of Welsh interest in the knock-out stages.
The English club appeared on course to clinch four points after staging a second-half comeback with tries from Niall Morris and Ben Youngs.
But the Ospreys, who had led for much of the game thanks to Joe Bearman's score, had other ideas and they salvaged a share of the points as Jonathan Spratt dived over at the death.
The draw sees the Ospreys bow out of Europe while next week's clash between Leicester and Toulouse will decide the outcome of Pool Two.
Following a lively start the Ospreys had the opportunity to open the scoring on nine minutes, after winning a penalty at the first scrum of the match, but Biggar struck the left upright.
The Ospreys fly-half was agonisingly off-target twice more before kicking the scoreboard into action on 28 minutes, following a sustained period of pressure.
Tandy's men continued to turn the screw and they stretched their lead to 10-points shortly after the hour mark as Bearman cantered over.
Fotuali'I and Tipuric combined to create the opening and the flanker found Ryan Bevington on the left.
The dynamic prop was unable to feed Richard Fussell but the ball was moved inside for Bearman to charge over.
Biggar added the extras before Flood responded with the Tigers' first points to bring the score to 10-3 at the interval.
Both teams threatened in a fiercely competitive return to play and the Ospreys almost added a second try.
Richard Fussell danced his way out of danger and launched a count-attack. He combined with Eli Walker, who chipped through and outpaced Niall Morris but was beaten by the bounce of the ball.
Following a scoreless 27 minutes the Tigers hit-back to level the scores. Toby Flood laid the foundations and Youngs sniped over from the base of the ruck.
Flood slotted the conversion to level the scores and within five minutes the visitors surged in front.
The Ospreys held their own at the scrum but the pressure eventually told and Morris dived over in the corner.
Flood missed the ensuing conversion but the try had handed the visitors a five-point lead with seven minutes to spare.
But the thrilling encounter was far from over and an electric break from Walker handed the Ospreys a lifeline.
The red-hot wing failed to find support but the ball was quickly recycled and Fotuali'I sent Spratt diving over.
Biggar had the chance to boot the Ospreys into the lead but he pushed his effort narrowly wide as the two sides settled for a draw.