Dutch defender Dustley Mulder, Brazilian midfielder Ramon Lopes, Portuguese winger Cristovao Ramos and Portuguese striker Joao Silva, considered as some of Levski's top players, are no longer part of the team, the club's chief executive said.
"It"s my decision, we can't achieve our goals with these players," Nasko Sirakov said. "I gave them a chance in the last two months but they didn't take it.
"We'll replace them and we're already negotiating with new players."
Last month, Levski sacked coach Nikolay Mitov and turned to Serbian Slavisa Jokanovic, who won the league titles with Partizan Belgrade and the Thailand title with Muangthong United last season.
Levski, the 26-times Bulgarian champions, were knocked out of the Europa League by unfancied Kazakhstan side Irtysh Pavlodar 2-0 on aggregate.
However, The Blues continued to struggle after the coaching change and won only one of their first four league matches under former Chelsea midfielder Jokanovic, who recently complained about the quality of the squad.