Slavoljub Muslin’s side lead Group D on goal difference over Ireland and the manager has implored his players to reinforce their position as automatic qualifiers for Russia next year by extracting full points.
The Serbians host basement side Moldova in Belgrade on Saturday, September 2 before travelling to Dublin for a crucial meeting with Ireland three days later.
Ljajic, who played for Fiorentina and Roma before joining fellow Serie A outfit Torina last year, had been a controversial omission in the campaign but sufficiently impressed Muslin in recent weeks to lose his outcast status.
Attack has been the most fruitful department for the Serbs to date in the qualifiers, with English Premier League duo Dusan Tadic and Aleksandar Mitrovic supplying goals at critical stages along their route to the summit.
Filip Kostic, the Hamburg frontman, may be in most in danger of losing out to the returning Ljajic.
Crystal Palace midfielder Luka Milivojevic and first-choice goalkeeper Vladimir Stojkovic will both miss the first game due to suspension and return for the Ireland duel.
Manchester United’s new recruit Nemanja Matic is one of four Serbians one booking away from being banned for the Dublin assignment.
“This group may go to the last games in October but these two matches are very important,” said Muslin.
“The players have played well enough to get into a good position and they are capable of keeping first place by getting six points from this double-header.”
Vladimir Stojkovic, Aleksandar Jovanovic (Partizan), Predrag Rajkovic (Maccabi Haifa), Marko Dmitrovic (Eibar).
Branislav Ivanovic (Zenit), Jagos Vukovic (Olympiacos), Stefan Mitrovic (Gent), Nikola Maksimovic (Napoli), Matija Nastasic (Schalke), Aleksandar Kolarov (Roma), Uros Spajic (Anderleht), Ivan Obradovic (Anderlecht), Antonio Rukavina (Villarreal).
Ljubomir Fejsa (Benfica), Luka Milivojevic (Crystal Palace), Nemanja Matic (Manchester United), Nemanja Gudelj (Tijandin Teda, China), Nemanja Maksimovic (Valencia).
Dusan Tadic (Southampton), Filip Kostic (Hamburg), Adem Ljajic (Torino), Aleksandar Mitrovic (Newcastle Utd), Andrija Pavlovic (Copenhagen), Mijat Gacinovic (Eintracht Frankfurt), Aleksandar Prijovic (PAOK).