Blues (8) 17
Williams crossed for the first try of the Magners League season
Tries: R Williams
Pens: Robinson (4)
Ospreys (9) 15
Pens: Connor (5)
*Highlights online Saturday, BBC Two Wales Sunday
The Blues opened the Magners League season with a revenge win over the side that pipped them to the 2006-7 title.
The siege-gun penalty kicking of fly-halves Nicky Robinson and Shaun Connor dominated a physical encounter.
On the stroke of half-time a dynamic Blues attack saw Maama Molitika put Rhys Williams in for the only try.
The home pack took charge as Connor kicked superbly to keep the Ospreys in touch, but he blew the shortest and last penalty to cost his team the win.
The visitors were missing 12 players to World Cup duty and the Blues six, but there was no motivation lacking, the Ospreys having won the final game of last season to overhaul the Cardiff side at the top of the league.
After a stong opening at the Arms Park with debutant Paul Tito to the fore, the Blues got on the board with a Robinson penalty.
The usual rusty, early season errors proceeded to dominate, but Connor's kicking leg was well-oiled, the outside-half sneaking the visitors into the lead with two superb, long-range penalties.
Connor kicked superbly - but his final kick will be remembered
Connor is not renowned for the length of his kicks, but his confidence was such that he teed up a third penalty from inside his own half - and landed it with something to spare.
The Blues hit back with the last move of the half, Gareth Williams and Jason Spice combining well to get the Opsreys on the back foot.
The threat in the right corner was just snuffed out, but Robinson swiftly spun the ball to the opposite wing where he found Molitika.
The flanker - who returned in the summer for his second spell at the Arms Park - off-loaded superbly in the tackle, Rhys Williams on his shoulder to scamper in for the first try of the season.
Robinson fluffed the conversion, but put his side ahead with a 50m penalty at the start of the second half.
With coach Dai Young this week touted as a member of the Lions staff in 2009, the Blues pack took a firm grip at the scrum and disrupted the visitors' line-out ball.
The Cardiff side continued to string the attacks together and tempted Andrew Millward to come offside at a ruck.
We were by far the better team
The veteran prop was yellow-carded and Robinson's third penalty soon afterwards extended the Blues' lead to 14-9, but Connor immediately responded with another 50m kick.
The Ospreys' infringements at the breakdown continued to cost them, Robinson landing another difficult kick in the 60th minute.
Another mighty Connor kick brought the west Glamorgan team back to within two points, though, as Young's team stuttered near the finishing line.
In the dying seconds, youngster Jamie Roberts was harshly pulled up for an early tackle as the Ospreys mounted a final, desperate attack.
Connor stepped up to the 35m penalty from a kindly angle, but with glory beckoning he scuffed his effort horribly wide.
The Blues' victory was their 16th home league win on the bounce, breaking the record held by Leinster.
Blues coach Dai Young:
"That was justice at the end, we were by far the better team.
"First and foremost I'm pleased with the win and we controlled it up front, but we need to improve on our performance.
"I was disappointed with our game management and we were our own worst enemies at times.
"We were going for kicks and drop goals and seemed to have no idea how to run down the clock."
Ospreys coach Lyn Jones:
"The result is obviously disappointing, but there was good intent to play from us when we had the ball.
"Our set piece went well up to the break, but then the Blues came out with a different mind set in the second half.
"We need to work on that area and we'll be fine for the rest of the year.
"Connor was excellent on limited possession and kicked like a dream, but everybody misses one."
Blues: Blair, R. Williams, Selley, Hewitt, J. Roberts, N. Robinson, Spice, Yapp, G. Williams, G. Powell, Jones, Tito, Molitika, Sowden-Taylor, Rush.
Replacements: Sidoli for Tito (76). Not Used: Stcherbina, Macleod, Rees, S. Roberts, Johnson, Lewis.
Ospreys: Byrne, Terblanche, Taylor, A. Bishop, Brew, Connor, Marshall, James, Hibbard, A. Millward, A. Millward, Cockbain, Collins, Lloyd, Pugh, Tiatia.
Replacements: Vaughton for Brew (47), B. Williams for Hibbard (61), Griffiths for A. Millward (67), Griffiths for A. Millward (67), Powell for Collins (67), Lewis for Pugh (62). Not Used: Spratt, Roberts.
Referee: Tim Hayes (WRU)
Neil Ballard was the video referee for the match, the first such official in the history of the Magners League.