Rasiak is sidelined with a groin strain that will see him miss the next month of Watford's quest to ensure their status in the Championship.
Manager Brendan Rodgers could be woefully short of firepower in attack as Tommy Smith faces a late fitness test on an injured knee that has ruled him out of the Hornets' last two games.
However, defender Jay DeMerit is back in training after a slight calf problem that saw him substituted against Crystal Palace recently, with Rodgers still undecided on what part the American will play at Ninian Park.
Fellow defender Jon Harley will play no part after he was booked for the 10th time this season and begins a two-game suspension.
Mart Poom (shoulder) and Gareth Williams (cruciate ligaments) are still unavailable.
Jay Bothroyd must prove his fitness before being considered for Cardiff.
The striker returned from a calf problem to play 69 minutes of Sunday's derby draw at Bristol City but he looked uneasy at times and, although the muscle has fully healed, he will be assessed in the lead-up to the game to ensure all the tightness has disappeared.
Ross McCormack came off the bench to grab a dramatic late equaliser at Ashton Gate and he would more than likely be the man called upon should Bothroyd not make it, although Eddie Johnson has also impressed of late.
Tony Capaldi is likely to continue at full-back in place of Mark Kennedy, who is still struggling with a hamstring injury.
On-loan goalkeeper Stuart Taylor will keep his place after impressing on his debut while Stephen McPhail should keep his place in central midfield after making his first start since November.
Winger Quincy Owusu-Abeyie is also pushing for a recall to Dave Jones' matchday 16.
Sporting Life