It was a frenetic, helter-skelter start, both teams throwing the ball around at any opportunity with no real pattern to the opening exchanges. Saracens spurned the chance to go for the posts after Shane Williams was guilty of holding on, opting to go to the corner from the 10m line, obviously fancying their chances of a repeat of last Saturday's early try at Wembley.

While they were unable to find a way through the Ospreys defence on this occasion, a second penalty decision went their way on the 22, and this time Farrell took the points to give his team the lead with six minutes gone.

After the problems at the scrum last weekend the Ospreys had the upper hand at the first couple of set-pieces this time around, and it was from a penalty to the Ospreys from a Sarries put-in that Dan Biggar was able to level things, after an exchange of pleasantries between the front rows, before Farrell was able to nudge his team back in front after Richard Fussell and Shane Williams had got themselves in a muddle dealing with a hopeful up and under on their 10m line, Sarries pressure eventually resulting in a penalty.

With the first half at the midway point the Ospreys were able to apply some pressure on the Saracens line through a series of scrums, the contest boiling over following the third penalty award to the hosts. As the noise levels raised up a notch or two, Matt Stevens and Paul James were given a long talking to by referee Jerome Garces, before the Frenchman gave the next decision to Saracens, penalising Rhys Webb for delaying the put-in as the scrum wheeled.

The Ospreys kept up the pressure though, and after a promising move that saw Andrew Bishop, Richard Hibbard and Shane Ashley Beck all heavily involved finally came to nothing, a penalty for offside allowed Biggar to level it.

Saracens struck back straight away, Biggar's clearing klck from inside the 22 after the Ospreys had secured the ball at the restart was charged down by his opposite number Charlie Hodgson and fell invitingly for Ernst Joubert to gather and score, Farrell converting.

Unperturbed the Ospreys continues to take the game to Saracens, Biggar's delicate kick to the wing just bouncing the wrong way for Tommy Bowe, before a well worked move saw Williams trying to feed Beck up the flank, Saracens defence forcing him into touch as he tried to offload.

Biggar had the chance to reduce the deficit after Saracens were pinged for not rolling away but his attempt from a central position 40m out was off target.

Farrell had better luck at the other end, a simple kick from in front of the posts after an offence by Adam Jones allowing him to take his team 10 points clear.

After the early dominance in the scrum it had descended into a farce once again, and Monsieur Garces drew the wrath of the Ospreys crowd when he sent Paul James to the sinbin after awarding Saracens a penalty as the setpiece went down on halfway.

HALF-TIME: OSPREYS 6 SARACENS 16

The Ospreys Heineken Cup hopes were on the line and they needed a positive start to the second half, but Biggar was unable to oblige, sending an early penalty from the right touchline across the face of the posts and wide of the left upright.

Despite being a man short the Ospreys stayed on the front foot, and after quick lineout ball allowed Ryan Jones and Hibbard to gain some hard yards, the ball was slipped wide to Beck who looked to dance his way over only to be hauled down inches from the line. The decision was referred to the TMO, and although a try decision looked unlikely, an attacking scrum five was the expected outcome, only for the verdict to be Sarries penalty for a double movement by Beck, allowing them to clear.

No sooner were the Ospreys back up to 15, Saracens were a man down, Schalk Brits yellow carded after an offence at - you've guessed it - the scrum!

Buoyed by the extra man the Ospreys roared into the opposition, Bishop's long miss-pass finding Beck on the wing who skipped through three tackles before Farrell was able to drag him into touch a metre short.

The game was being played out almost entirely in the Saracens half now, and almost as soon as Brits re-entered the action, his team-mate Kelly Brown was sent to the bin for a cynical trip on Biggar as he chased his own grubber.

The Ospreys made the most of their extra man this time, working the ball the width of the field, left and then back to the right. Williams ignored Ian Evans who was on his own on the touchline to come back infield, but eventually the long pass was flung to the unlikely figure of Ian Gough who crashed over in the corner, the TMO confirming his try. Biggar's excellent conversion brought the scoreline to 16-13 in Saracens favour with under 15 minutes left on the clock.

It was gripping stuff, and the game was delicately poised as it entered the last 10 minutes. Farrell had a chance to take the Saracens a converted try clear but he missed what seemed a straightforward kick, giving the Ospreys one last chance, but Saracens held firm to secure a memorable win for them, condemning the Ospreys to their first European defeat at home in 18 matches.