The Serbia side, made up of home-based players, produced an impressive performance in Osaka, particularly the league's top scorer Mrdja who fired the visitors into a 2-0 lead before winger Nemanja Tomic added the third.
Mrdja scored his first two international goals in his third appearance for Serbia and goalkeeper Zeljko Brkic, his Vojvodina Novi Sad team-mate, was equally outstanding.
"There is no question they both deserve to be in the World Cup squad and I think Brkic has shown that he should be the first-choice goalkeeper," Vojvodina coach Milan Djuricic told Reuters by telephone.
"Mrdja, on the other hand, is exactly what Serbia need up front to boost their firepower and I am glad his hard work has been rewarded with a clinical brace against Japan.
"The overall performance shows there is plenty of talent in the Serbian top flight and the league's quality is often underestimated because of meagre crowds.
"The lads were obviously motivated in front of a packed stadium in Osaka and I am sure Antic will have seen the potential these players have got."
STRUGGLING EXILES
Serbia's impressive qualifying campaign in Europe's Group Seven was based on the flair and experience of their exiles, with only a handful of home-based talent playing any part in their run to the June 11-July 11 event in South Africa.
But some of coach Radomir Antic's first-choice players are struggling at their clubs, notably goalkeeper Vladimir Stojkovic who is on loan at Wigan and the inconsistent strikers.
Nikola Zigic and Marko Pantelic are both playing in fits and starts while Danko Lazovic is still getting used to life in the Russian first division at Zenit St. Petersburg.
Although Serbia have a solid back four marshalled by Manchester United centre back Nemanja Vidic, good performances by Marko Lomic in the Serbian league suggest the versatile left back could add much-needed depth in that department.
Partizan Belgrade coach Goran Stevanovic backed Lomic to break into the national team after two goals and six assists for the Serbian champions since the league restarted from its December-February break.
"Lomic has been in outstanding form in the last two months and he is ready to take his place in the World Cup squad," Stevanovic told Belgrade media.
"Several other Partizan players have also done very well and it's very encouraging that Antic has plenty to choose from."
Serbia are drawn in Group D for the World Cup with Germany, Australia and Ghana.
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