ADELAIDE United's stuttering Asian Champions League campaign may have hit yet another stumbling block after questions were raised over Cassio's eligibility to play last night.
The fullback took to the field against Indonesian side Persipura Jayapura in last night's sudden death play-off for a place in the group stage of the ACL after the Court for Arbitration in Sport ordered the game to take place.
But in Adelaide's last appearance in the ACL, in the 2010 knockout phase when they were beaten 3-2 by Jeonbuk Motors, Cassio was red carded after receiving two yellows.
A mandatory one match ban should have followed his dismissal under AFC regulations, although Article 38.2.c is vague about whether that is served in the ACL, or domestically if it came at the end of a club's ACL campaign as Cassio's did.
However Cassio also played in Adelaide's next competitive A-League match following the Jeonbuk clash, when he appeared against Newcastle Jets in the first round of the 2010/11 season.
By also playing for the Reds again last night, Cassio appears to have escaped any suspension for his dismissal - and as a result may not have been eligible to appear for Adelaide last night.
Since Cassio's sending off, the club has changed ownership and the coaching staff has been replaced, meaning the ban could possibly have been overlooked or not known about by the new administration.
But it could now cost the club its hard-earned place in the Champions League.
Adelaide's route back to the ACL has been torturous after the Asian Football Confederation initially rewarded them with a play-off spot in the competition for coming third in the A-League last season.
But the AFC then blocked play-off opponents Persipura from taking part in the competition as they were from the rebel Indonesian Super League currently in dispute with the confederation.
Adelaide appeared set to go straight into the group stage of the competition and were drawn in Group E until Persipura then took the matter to CAS who upheld their case earlier this month, subject to an appeal.
A single leg, sudden death play-off was hastily convened at short notice for Hindmarsh which Adelaide won 3-0 last night.
However the new doubts over Cassio's eligibility could bring Adelaide's ACL campaign to yet another grinding halt with a new level of confusion.
If Cassio should have been banned from last night's game, the AFC may order a re-match or simply reverse the scoreline to hand the win to Persipura, giving them qualification to the group stage instead of the Reds.
Even if the AFC rules that the ban should have been served domestically, any subsequent A-League points deduction could jeopardise Adelaide's third place finish in the 2010/11 A-League that earned them the play-off spot.
Gold Coast United ended the season four points behind the Reds in fourth place, and a significant points deduction for fielding an ineligible player in the A-League could see the Queenslanders leapfrogging Adelaide into the ACL play-off spot instead.
Alternatively, if the AFC take no action, Persipura may return to the CAS over Cassio being fielded when he shouldn't have been.
Both Adelaide United and FFA refused to comment on the speculation.
However coach John Kosmina was earlier relieved to have finally got the play-off and associated legal action apparently out the way, with a clear path to the group stage now seemingly opening up to them.
He added: “It’s over and done with once and for all now, any appeal process is null and void.
"It's a good thing and it’s a good feeling."