The Ospreys U18s fell to defeat at St Helens on Tuesday in their penultimate WRU Regional Age Grade game of the season, the Blues completing the double over the Eyasses.
It was the home team who started strongly and took an early lead, scrum half Connor Tantum touching down for the first try with only four minutes on the clock, Cai Evans adding the extras to give the Eyasses a 7-0 lead.
The Blues hit back to level through an Alun Lawrence try and Ben Thomas conversion on 17 minutes, only for the hosts to retake the lead through the boot of Evans eight minutes later.
The turning point came a minute before the break when Ospreys centre Ewan Gully was penalised and shown yellow for persistent team offending. Thomas leveled things before, with the hosts still a man short, the Blues took the lead at the start of the second half, blindside Lawrence getting his second of the nght, Thomas adding the extras.
Scrum half Dane Blacker then stretched the lead, Thomas again converting, to put the Blues 24-10 to the good. With time up the Blues then scored a fourth, replacement Garyn Payne going over. Thomas completed the scoring to make it five from five on a good night for the visitors.
The Ospreys U18s play their final game next Wednesday against the Dragons.