Brisbane Roar coach Mike Mulvey's uncertain future with the struggling A-League champions has darkened further following their Asian Champions League failure in Thailand.Mulvey has an iron-clad agreement to finish this A-League season with Brisbane but his hopes of continuing with the club in 2013-14 took a major hit with Wednesday's ACL qualifying defeat.The Roar lost 3-0 to Thai FA Cup champions Buriram on penalties after a scoreless 120 minutes in hot and humid conditions.The Roar, who flew to Thailand following their 2-1 loss to Sydney FC on Sunday, showed plenty of character to hang in the match despite being largely outplayed by the home side at Thunder Castle Stadium.But the sudden-death playoff was epitomised by Brisbane failing to convert any of their three penalty attempts as Buriram goalkeeper Sivaruck Tedsungnoen made a string of saves.The loss was another tormenting blow in a horror season for the two-time champions, occurring the same day skipper Matt Smith was ruled out for the rest of 2012-13 following hip surgery.Mulvey, who replaced Rado Vidosic as coach in December, was already under immense pressure with the club sitting eighth on the A-League table and looking a shadow of the side that dominated under Ange Postecoglou.Brisbane's results in the ACL group stages were to be a key factor in whether the club's owners, the Indonesia-based Bakrie Group, would renew his contract.Despite creating few genuine chances against a sharp and energetic Buriram outfit, Mulvey defended the result and was full of praise for his side's effort in trying conditions."It's not easy when you lose on penalties but c'est la vie," Mulvey told AAP. "Penalties are a lottery but that first save (by Sivaruck) was world class."Let me tell you that this team (Buriram) is a good side and they would acquit themselves very well in the A-League."Mulvey also defended his long wait in using James Meyer and Steven Lustica as substitutes, only replacing Luke Brattan and Stef Nijland - two of the Roar's better players - late into extra-time.The Roar arrive back in Brisbane on Friday morning and must rebound immediately against Wellington at Suncorp Stadium on Sunday to strengthen their top-six hopes.They have been boosted by the availability of striker Henrique (quad) and midfielder Massimo Murdocca (ankle) but might be without fullback Ivan Franjic who was concussed in the first half in Buriram."We understandably have some very tired boys right now, but there is a real steel and determination to go to Suncorp Stadium on Sunday and secure a positive result," Mulvey said."Every Brisbane Roar fan can be proud of the effort their team showed against Buriram."Every single player gave everything they had for the shirt, the club and the fans."