The former New Zealand full-back made his first appearance in 15 months after battling back from a career-threatening knee injury.
Blair got the scoreboard ticking over for the visitors after just two minutes at Kingsholm but that was all the youthful side could manage as the English club ran riot.
Former Newport flanker Peter Buxton opened the scoring for the Cherry and Whites with a well taken try set-up by England Six Nations hopeful Henry Trinder.
Tim Molenaar grabbed a second touch down to hand his side a 21-3 lead at the interval.
Cardiff held Gloucester for 25 minutes of the second-half but the pressure eventually told and former England wing James Simpson-Daniel pounced for a pair of tries before Andy Hazell completed the rout.
The Blues had made 13 changes to the starting line-up that faced Racing Metro last week with Chris Czekaj the sole survivor. They featured three Wales under-20 internationals and a host of academy products.
The youthful outfit continued fighting to the death and Tom James was unlucky not to score in the final minute.
