Veteran forward Lehlohonolo Majoro was given a start up front as Thembela Sikhakhane also got a run at the back as the KwaZulu-Natal were looking to improve their survival fortunes.
Majoro justified his inclusion six minutes from kick-off after steering home his Bonginkosi Ntuli's well-weighted delivery around the area for the game's opening goal.
Celtic struggled to spring to life following the earlier exchanges, as the hosts peppered in more shots at Chaine who needed to deny Sandile Khumalo before the half-hour mark.
The hosts, who controlled the opening quarter, were made to pay for their profligacy after 41 minutes when Motebang Sera brought Siwelele Sa Masele all square, adding to the two goals he scored against.
Usuthu gallantly surged forward after halftime and found the back of the net with a header from Khumalo, but it was chalked off for offside.
Ayanda Dlamini turned to the bench on 57 minutes and opted to introduce Talent Chawapihwa for Jabulani Ncobeni, with the home side steadily leaning towards a second goal.
Their second goal arrived six minutes later when a throw-in deep into visitors half landed unkindly to Celtic defender Wandisile Letlabika who slotted the ball into his own net.
Celtic, however, levelled matters once again in the 68th minute when captain Ndumiso Mabena showed face to beat Usuthu shot-stopper Siyabonga Mbatha.
Usuthu almost regained the lead late on through substitute Charlie Hlalele, but Chaine's finger-tips denied him an immediate impact as it finished all square.
AmaZulu: Mbatha, Gumede, Sikhakhane, Mabiliso, Khumalo, Sithebe, Ncube, Ncobeni, Magubane, Majoro, Ntuli,
Subs: Boshoff, Masilela, Magaqa, Darpoh, Chawapihwa, Ngubane, Maduna, Hlalele, De Jong.
Celtic: Chaine, Letlabika, Mahashe, Letsoalo, Mabena, Chabalala, Sera, Fikizolo, Phalane, Baloyi, Ngobeni.
Subs: Mabokgwane, Mashikinya, Luthuli, Maema, Potsane, De Jongh, Lingwati, Masuku, Tchilimbou.