The Blues had to overcome a stuttering lineout and appalling weather conditions to record their derby win to move up from ninth to seventh in the points table as the Dragons remain in 11th.
The Dragons will be bitterly disappointed not to have stolen a victory as they played most of the rugby and in Andy Tuilagi and Toby Faletau they had the two standout players on show.
Going into the match, the Blues made a number of changes in the forwards with two changes in the front row – hooker Rhys Williams coming in for Marc Breeze while Sam Hobbs replaced Taufa’ao Filise who moved to the bench.
Lou Reed replaced James Down in the second row and Robin Copeland replaced Josh Navidi on the blindside.
Faletau made a welcome return for the Dragons in a new look back-row which saw captain Lewis Evans switch to blindside with Nic Cudd coming in at openside.
Hooker Sam Parry has recovered from a dead leg to start while Will Harries, Andy Tuilagi, Phil Price and Nic Cudd also get the nod.
In a typical derby affair, there was a bit of niggle early on with both Hobbs and Scott Andrews getting on the wrong side of the Dragons.
Patchell, against the run of play, put the Blues in front in the 15th minute after Dragons winger Mike Poole was penalised for tackling Dafydd Hewitt without the ball. The Blues fly half calmly slotted the penalty after the Dragons had turned down two earlier opportunities themselves to take the lead.
Patchell doubled the lead in the 22nd minute after the Dragons were penalised at a ruck after a promising run by second row Andrew Coombes come to nothing.
In deteriorating conditions, both teams struggled to overcome the wind and rain on a heavy pitch.
Hallam Amos showed his inexperience when he took a quick throw-in to himself and then kicked the ball only to see the wind bring it back and put his entire team off-side. From wide out Patchell curled the ball in to make it 9-0 to the home side.
Dan Evans had the chance to reduce the arrears but he fired his shot wide from in front of the posts. Faletau and Tuilagi did their best to put the Dragons on the front foot with charging runs but the Blues repelled everything thrown at them.
Eventually the Dragons pressure told. Eight minutes after the re-start the visitors battered away at the Blues try-line. Tuilagi was put into space by Poole who brushed aside the challenge of Harry Robinson with ease before ploughing over in a fruitless double tackle by the Blues. With Wayne Evans adding the conversion the match was back in the melting pot.
Patchell was then isolated in the tackle to give away a penalty as the Blues tried to run their way out of trouble. Lewis Robling rammed over the shot to put the Dragons 9-10 in front. But Patchell made amends immediately from the re-start when the Dragons made a mess of the kick-off.
The Dragons then pounded away at the Blues but the home defence manfully withstood the pressure. Robling pushed a drop goal wide as the Blues defence hounded him down but the Dragons continued to pound away at the Blues try-line.
By hook or by crook, the Blues defence stubbornly denied the increasing frantic attempts by the Dragons to steal the win to gain bragging rights in the east Wales derby.
