Harbour's five game winning streak came to an end when it was beaten 19-16 by Taieri in a cliff hanger at Peter Johnstone Park today.
Harbour dominated territory and possession for the first 60 minutes but handling errors and a high penalty count proved its undoing.
Harbour needed the win to keep in touch with the top four teams.
But it is now six points adrift and it would be a surprise if this was caught up with only two games left before the semi-finals.
Taieri leads the Gallaway Trophy competition with 73 points and is followed by Southern 62, University A 54, Dunedin 54, Harbour 48, Alhambra-Union 41, Kaikorai 38, Zingari-Richmond 33, Green Island 6, Pirates 6.
Southern was too clinical and beat Alhambra-Union 31-22 at Bathgate Park. Its rushed defence stopped some promising Alhambra-Union attacks.
University A coasted to an easy 28-14 win over Pirates at the University Oval and Dunedin scored 10 tries when it beat Green Island 62-23 at Kettle Park.
Zingari-Richmond 27 Kaikorai 21; Southern 31 Alhambra-Union 22; University 28 Pirates 14; Taieri 19 Harbour 16; Dunedin 62 Green Island 23.