Cardiff Blues overcame ill-discipline to heap further misery on Ospreys with victory in a low-quality Welsh derby in Swansea.

The visitors had three players yellow-carded with Filo Paulo, Tomos Williams and Josh Adams sin-binned.

A second-half try from Jarrod Evans proved crucial before a late Jason Tovey penalty sealed the win.

Lacklustre Ospreys managed a penalty try and three penalties from Marty McKenzie.

Ospreys have suffered 11 defeats in 12 games this season and showed little attacking quality despite having a numerical advantage in periods of the game.

It was a first league win in Swansea for Cardiff Blues since 2005 with Wales squad flanker Shane Lewis-Hughes named man-of-the-match for his resilient defensive work.

Wales forward Justin Tipuric had returned to captain Ospreys in his first appearance for his region this season.

Scott Otten made his 100th appearance in a team showing six changes from the 40-27 loss against Racing 92 on 13 December.

Cardiff Blues made two changes from their defeat in Pau with prop Brad Thyer and ex-Osprey locks James Ratti starting.

Blues had hoped to have Wales flanker Josh Navidi back for the first time this season, but he had not fully recovered from the hamstring injury suffered in the World Cup quarter final win over France.

Penalty try and sin-bins

McKenzie opened the scoring before Jarrod Evans slotted over two kicks. Cardiff Blues' indiscipline cost them with two men yellow carded by referee Dan Jones.

Second-row Paulo was yellow carded for a needless off the ball challenge on Ospreys wing Hanno Dirksen while Tomos Williams was sin-binned for a high tackle on Dan Lydiate to prevent a try.

A penalty try was awarded to Ospreys for the latter incident as the hosts led 10-6 at half-time.

Blues lost another man to the sin-bin when Wales wing Josh Adams was shown a yellow card for a professional foul. His dismissal came just after the return of Paulo and before Williams left the the field.

Ospreys failed to capitalise on the numerical advantage as wing Dirksen was foiled at the right-hand corner. They had to be content with a penalty from McKenzie after a high tackle from Will Boyde on Aled Davies.

Quality rears its head

With the full complement on the field, Blues responded with a penalty for replacement Tovey to reduce the deficit to four points.

The first bit of real quality came from Cardiff Blues as scrum-half Tomos Williams chipped deftly over the top for Jarrod Evans to gather and score for the visitors opening try which Tovey converted.

Ospreys immediately levelled with another McKenzie penalty and Blues failed to score a second try when replacement flanker Olly Robinson dropped the ball with the line beckoning.

But Blues won a scrum penalty and Tovey slotted over the shot to give the visitors the lead again with seven minutes remaining.

It proved the match-winner in what a poor advert for Welsh regional rugby.

Cardiff Blues host Dragons on Boxing Day, while Ospreys travel to Scarlets on the same day.

Ospreys captain Justin Tipuric: "It was a tough day and we are better than that. There is no confidence in the team at the moment and we made a few mistakes.

"It is a club where we have strong characters and we have to go forward. We can't go much further back at the moment.

"It is just not there at the minute.

Cardiff Blues head coach John Mulvihill: "It was a game where we could have played a bit better but it just shows the character of the team when you are down to 13 for so long and they did not score many points in that time.

"It is a squad game because the boys who came on made a big improvement as well.

"We kept the pressure on and we are happy to get away with the win tonight."

Ospreys: Evans; Dirksen, Thomas-Wheeler, S Williams, Morgan; McKenzie, A Davies; Smith, Otten, Fia, Beard, B Davies, Lydiate, Tipuric (capt), Cracknell.

Replacements: Lake, Fawcett, Gardiner, Orie, Morris, Venter, Price, K Williams.

Blues: Morgan; Lane, Lee-Lo, Thomas, Adams; Evans, Williams; Thyer, Myhill, Andrews, Paulo, Ratti, Lewis-Hughes, Boyde (capt.), Turnbull

Replacements: Belcher, Gill, Assiratti, Cook, Robinson, Williams, Tovey, Amos

Referee: Dan Jones (Wales)

Assistants: Gareth Newman (Wales) & Chris Morgan (Wales)

TMO: Tim Hayes (Wales)