"Chirambadare should be deputising for George, but it' all up to George to do some introspection. He needs to provide the goods that will force Steve to use him regularly,” Nkosi told The Sowetan.
Lebese has struggled with injuries this season and Chirambadare has been able to cement his place in the Amakhosi starting line-up.
"He has ambition, potential and all the attributes that modern coaches want, but I can't seem to understand why he can't take his game elsewhere so he would play regularly for the national team to attract good teams in international leagues," Nkosi said.
The 28-year-old Lebese has made only 17 appearances in all competitions to date - netting three goals in the process.
The last time he played a full 90 minutes was when Amakhosi were held to a 1-1 draw by Cape Town City in a league game in November last year.