His old club Red Star Belgrade came calling in late summer 1999. Muslin took over the reins on 20 September, in difficult circumstances after Miloljub Ostojić got sacked because of poor league form and embarrassing 0–1 first leg "home" loss (match was played in Sofia due to air traffic embargo imposed on FR Yugoslavia following the NATO bombing that ended a couple of months earlier) to Montpellier HSC in UEFA Cup first round. Though he couldn't lead his squad past the French team in the second leg (his first match in charge), Muslin won the domestic double (league & cup) at the end of the season in an impressive fashion.