But The Borders registered a morale boosting victory as Geoff Cross snatched two tries at Netherdale as his side ran in 22-16 win.
Borders scored three tries to the Ospreys’ one, and defended well in the closing stages to deservedly come away with the points.
After the opening exchanges dominated by the home side, a short spell of Osprey pressure resulted in the Welshmen breaking the deadlock with a try in the 14th minute.
Flanker Gavin Thomas powered over after they made a strong pack drive from the line-out. Gavin Henson slotted the conversion.
Borders responded in positive fashion, gaining their reward for their hard work when Lock Colin Stewart made charge a charge into the 22 to set up Cross; first score.
Home outside-half Gareth Morton made amends for an earlier penalty miss by adding the extras – only to see Henson edging his side in front with a penalty just before the break.
Morton burst back into the spotlight to grab the second Borders try after a surge by Chris Cusiter.
Ospreys rallied with a further Henson penalty and a snap drop-goal from Shaun Connor.
But Borders were to seal the victory when Cross completed his double, Clark Laidlaw adding the conversion, and slotted a last-gasp penalty give the home fans some much needed cheer.
But there are further headaches for Ospreys boss Lyn Howells. His World Cup depleted and injury ravaged side have slipped to seventh in the table – having lead the division earlier in the season.