When Ospreys stepped out on the pitch at Cardiff City Stadium, all the mental arithmetic had been completed, the job was clear.

Win, with four tries or more, and they would continue their season into the play-offs.

Ospreys’ chances of finishing in the top eight of the United Rugby Championship had been calculated as low as 2% before this weekend but that would soon change.

Connacht fell on Friday night to Leinster, whilst Benetton secured their place by thrashing Edinburgh 31-6 ensuring the Scottish side left Italy without a losing bonus-point.

At the same time, Lions fell to a 29-24 defeat at 14-man Stormers meaning they were in eighth before a ball was kicked between Cardiff and Ospreys.

Ospreys were in 11^th but trailed Lions by five points, meaning they needed a bonus point win against Cardiff, their 10^th of the season, crucially one more than the number managed by Lions which would put them ahead of the South Africans in eighth.

All caught up? Right, onto the game itself.

Any suggestion Ospreys would focus solely on winning the game and not the bonus point seemed to be dispelled early on. Ospreys captain Justin Tipuric asking his fly-half to kick to touch early doors rather than go for posts.

The decision was justified however, after Keiran Williams went close, Nicky Smith, on what might have been his final appearance for Ospreys, bundled his way over inside seven minutes.

Cardiff, however, were intent on ensuring this wouldn’t be a procession for Ospreys and responded immediately.

Tinus de Beer wrapped around Ben Thomas before feeding Wales hopeful Theo Cabango, who showed good gas to beat wing rival Keelan Giles on the outside and reach out to score.

Sadly, Cabango was forced off barely two minutes later, slipping on the Cardiff City Stadium turf as he attempted to chase his own kick and appearing to pull his hamstring.

Both sides struggled to gain control for the next 15 minutes but then came one of Welsh regions’ tries of the season.

After Huw Sutton’s knock-on inside Cardiff’s 22, the home side looked to counter but Mason Grady’s clearing kick was gathered by Max Nagy and Ospreys’ response was devastating.

The fullback broke through initially and on the next phase, Jac Morgan went through a hole in midfield.

The ball was then spread wide to the left and little looked on when Giles received the ball but he made a half break before offloading speculatively to Dan Edwards who showcased good hands to gather before throwing a back door pass out to his captain Justin Tipuric who scored in the corner.

Cardiff’s Mason Grady came incredibly close to a response before half time, a victim of Cardiff City Stadium’s short in-goal area, he was unable to prevent Cameron Winnett’s grubber kick going dead in goal.

Not to be denied however and with seconds remaining in the half, Grady would get his score.

Evan Lloyd was found on the outside from a brilliant ball from Winnett, with the hooker showcasing good speed to burst down the touchline before feeding captain Thomas who was hauled down inches from the line by Owen Watkin.

Thomas offloaded off the floor and Grady fell over the line when he might have considered taking the ball closer to the posts to make the conversion an easier one for de Beer who ultimately missed the kick leaving the scores level at half time.

Ospreys began the second half the stronger, a brilliant James Botham turnover halting one attack but minutes later they would have their third.

After Dewi Lake went close from a driving maul Ospreys went over through Smith again from short range. Additionally, Ben Donnell saw yellow for a transgression in the maul leaving Cardiff down to 14.

Once again, Cardiff responded well. Good hands from Ben Thomas and Cameron Winnett put Lloyd through a hole but, with Shane Lewis-Hughes on his outside, he showed a dummy and was dragged down by Max Nagy who was perhaps fortunate to avoid a yellow card after cynically stopping the ball coming back.

Thomas kicked the resulting penalty having taken over kicking duties after de Beer had been forced off with injury and Cardiff managed their period down a man well, despite Thomas missing another penalty soon after.

Crucially Ospreys would get their fourth however. From a high kick, Edwards did brilliantly to avoid the clutches of Grady before kicking ahead and when Thomas fumbled the ball in-goal, Ospreys were presented with a scrum five metres out.

After their first effort on penalty advantage was repelled, Ospreys opted for the scrum again and this time they were successful as Edwards’ cut-out pass found Luke Morgan who had a walk-in for Ospreys’ crucial fourth try.

Bonus point secure, now time to secure the game from an Ospreys perspective.

That task looked as though it was about to become immediately more difficult when Gabriel Hamer-Webb kicked on and chased his own kick only to knock the ball on with the try-line at his mercy.

Ospreys fans might have been forgiven for thinking luck was on their side but Cardiff weren’t finished and came again with Thomas the creator, stepping inside and outside both Nagy and Giles before offloading to Hamer-Webb to score.

Thomas converted the kick to leave just four points in it going into the final 10 minutes.

With minutes remaining Cardiff appeared to have momentum only for substitute Seb Davies see red for a high shot on Ospreys centre Watkin.

Ospreys kicked to the corner and secured the result with their fifth try. Their driving maul looked destined for the try line only for Rory Thornton to drag the maul down and referee Adam Jones showed no hesitancy in running under the sticks for a penalty try.

As they had throughout the game, Cardiff fought back immediately and when Rey Lee-Lo was stopped short, substitute Luke Davies became the fourth player to receive a card for cynically stopping the ball from coming out of the ruck.

With the clock in the red, Thomas’ brilliant pass found Grady out wide who powered over for his second try of the game and yet another losing bonus point for the capital region but it was the Ospreys who’d celebrate an improbable top eight finish.

Cardiff: (12) Tries: Cabango, Grady x2, Hamer-Webb, Con: de Beer, Thomas x2, Pen: Thomas.

Ospreys: (12) Tries: Smith x2, Tipuric, L. Morgan, Penalty, Con: Edwards x3.

Cardiff: Winnett (Beatham 65mins); Cabango (Hamer-Webb 14mins), Lee-Lo, Thomas, Grady; de Beer (Halaholo 45mins), Bevan; Carré (Domachowski 48mins), Lloyd (Daniel 65mins), Assiratti (Litterick 48mins), Lewis-Hughes (S. Davies 65mins), Thornton, Donnell, Botham, Lawrence (Timani 59mins).

Ospreys: Nagy; L. Morgan, Watkin, K. Williams, Giles (Houston 72mins); Edwards (O. Williams 75mins), Morgan-Williams; Smith (Thomas 54mins), Lake (Parry 61mins), Botha (Henry 54mins), Ratti, Sutton, J. Morgan, Tipuric, Morris (Deaves 72mins).