Tito picked up a knee strain, and his inclusion in the squad that travel to Kingsholm for Sunday's crunch Heineken Cup clash is unlikely, according to Young who told the Western Mail: "Paul is very, very doubtful.
"It's very unlikely he will be fit for the Gloucester game, but he should be fit for the visit of Calvisano."
But Young has been told the injury will not keep Tito out of action for long. He explained: "It isn't a long-term problem, but he has strained his medial ligament in his knee."
The Blues still have work to do to qualify from Pool Six of the Heineken Cup and repeat last season's achievement of reaching the final eight.
Home advantage is crucial in European competition - as the Blues learnt when they were defeated by Toulouse last year. And the winners of the Kingsholm clash look likely to secure top spot and a home draw for the quarter-finals.
Cardiff have won all four of their matches to date, and have 18 points, meaning they sit top of the Pool - but have not yet confirmed their quarter-final qualification. They host Calvisano in the final match and would expect to take maxiumum points against a side who have failed to win a Heineken Cup match this season.
Gloucester's only defeat was at the hands of the Blues in Round 2, Cardiff "won ugly" on that day, according to Young. They would take another ugly result on Sunday.