The Ospreys dug deep, though, and Spice's 80th-minute try gave them a six-point lead they were never going to give up - despite nearly seven minutes of injury time. With several potential British Lions tourists on show, the match had all the makings of a late Christmas cracker, but the wind, rain and plummeting temperatures turned the Arms Park into a rice paddy and both sides' handling suffered as a result.
Blues fly-half Nick Macleod opened the scoring with a well-struck goal into the teeth of the wind in the 25th minute, but the home fans' glee lasted barely 30 seconds. Blues winger Jonny Vaughton sent a suicidal pass over the head of Macleod on his own try-line and Ospreys flanker Richie Pugh dived on the loose ball.
Ospreys fly-half Matthew Jones then cynically and illegally prevented an almost certain Blues try by walking through a ruck and toeing the ball ahead. Some good work from skipper Martyn Williams had set up the position and Macleod converted the penalty as Jones trudged off to the sin-bin. Some more blatant offside play from the Ospreys gave Macleod the chance to give his side the lead, and he made no mistake, but there was enough time left for Gavin Henson to return the favour and the visitors led 10-9 at the break.
The Blues had their chances in the second spell, but looked tired and disjointed in the terrible conditions. The Ospreys kept the ball close and attacked the home side's line for much of the half. It paid off when Spice squeezed over in the corner and the Blues had to be content with yet another losing bonus point.
Blues: R Williams; J Vaughton, T Shanklin, T Davies, C Morgan; N Macleod, R Powell; G Jenkins, R Thomas (G Williams 79), B Evans (J Yapp 66), D Jones (C Quinnell 58-60, 66), R Sidoli (N Budgett 79), K Schubert, J Malpas (N Thomas 43), M Williams (capt)
Scorers: Pens - N Macleod 3.
Ospreys: A Durston; E Seveali'i, S Parker (D Bishop 59), G Henson, S Williams; M Jones, J Spice; P James (D Jones 53), B Williams (capt), A Jones (A Millward 59), B Cockbain (A Newman 53), J Thomas, A Lloyd (J Bater 63), R Jones, R Pugh
Scorers: Tries - R Pugh, J Spice; Pen - G Henson; Con - G Henson
Halftime: Ospreys 10-9
Yellow Card: M Jones (Ospreys)
Referee: Nigel Owens (WRU)