An own goal from Ramahlwe Mphahlele after 18 minutes at the FNB Stadium handed Amakhosi the lead, before Tshepang Moremi found a quick-fire equaliser, a mere five minutes later.
Elmo Kambindu then put Usuthu into the lead on the hour mark, only for an error by AmaZulu goalkeeper Richard Ofori to hand Chiefs a share of the spoils when he fumbled the ball into to own net with 63 minutes played.
Tashreeq Morris, Glody Lilepo and Thabo Cele all started the game, with Morris and Lilepo both involved in Chiefs' goals.
Speaking after the game, Nabi told SuperSport: "I am happy with Tashreeq and even Lilepo and Cele.
"You saw with the two goals scored, one was Tashreeq and the second was Lilepo.
"Even Cele, before he tired was bringing a lot of fluidity and smartness. Lilepo, Tashreeq and even Thabo were tired in the second half. We felt that with more preparation they could even have helped more. But we feel the three signings are very good and can help us a lot."
Next up for Chiefs is a trip to face Stellenbosch at Athlone Stadium on Friday.
Nabi added: “We feel it is a game we deserved to win with all the opportunities we had, although our opponent also had some opportunities.”
Despite another painful domestic cup exit, Kaizer Chiefs co-coach Cedric Kaze insists the club's season is far from derailed, with the Betway Premiership title race and CAF Confederation Cup still firmly within reach.
Kaizer Chiefs will aim to seize control of their CAF Confederation Cup fate when they host Al Masry in a decisive Group D encounter at the New Peter Mokaba Stadium on Sunday.
Mamelodi Sundowns prepare for a decisive CAF Champions League Group C clash against Saint-Eloi Lupopo on Sunday at Stade TP Mazembe.
Asanele Velebayi says the weight of wearing the Kaizer Chiefs badge has sharpened his focus and reshaped his mindset.
