If Adelaide United cannot beat the Central Coast Mariners by two goals at Gosford on Sunday night they will lose the A-League minor premiership.The harsh arithmetic of Adelaide's position was confirmed by Melbourne Victory's nervy but ultimately comfortable 2-0 win over Wellington Phoenix at home, a result that made it impossible for the Reds to stumble their way to the title, and the first of two Asian Champions League places.As they prepared to travel east, Adelaide's players acknowledged their position was a fair test of their eligibility for a trophy in 2008-09, and that defeat would mean they did not deserve to finish top despite sitting there for much of the season."Definitely, if you want to finish top you have to win the hard games and we've got to start doing that in the finals, so why not start in round 21?" United 'keeper Eugene Galekovic said."We've had the week off so there's no excuse this week."I think during the season at times it was tough but right now the boys are fresh and have only the A-League to worry about."For all their achievements on multiple fronts in Asia, a loss, draw or even a narrow victory against Lawrie McKinna's men would mean the Reds have been unable to register a single victory over either the perennially competitive Mariners or title rivals Melbourne this season - hardly the credentials of a champion side.One thing now in favour of the Reds is that Melbourne's defeat of Wellington also served to shore up the Mariners' top four spot, meaning they will take part in the play-offs regardless of what unfolds on Sunday night.The home side will be missing Dean Heffernan and Andrew Clark through suspension, meaning one time United playmaker Greg Owens may get the chance to play spoiler against his former club.Adelaide also have personnel concerns, defensive cornerstone Sasa Ognenovski banned for the match while doubt lingers over Alemao (groin) and Robert Cornthwaite (hip).Cassio, Lucas Pantelis and Kristian Sarkies return to add speed and creativity to the Reds midfield.Regardless of the players at his disposal, Reds coach Aurelio Vidmar said his team had the right mix of confidence and nerves about them."There's a lot of urgency and everyone knows the scenario, what it means to each individual and also for the club," he said."It's a big day, a big game and hopefully we can get over the line."We haven't beaten Central Coast. We had a great hour here (at Hindmarsh), leading 3-0 then drew 3-3, and got battered over there 3-0, so it's not going to be an easy game."