Chiefs coach Ian Foster is calling for a more clinical approach from his side for Friday night's Super Rugby clash with the NSW Waratahs in Sydney.

Foster has made two changes to his starting lineup from last start 16-13 loss to the Blues, summoning Dwayne Sweeney from the bench for former All Blacks skipper Tana Umaga at inside centre to partner Richard Kahui in the midfield, while Toby Smith replaces Sona Taumalolo at loosehead prop.

With just two wins after six rounds planting them at the bottom of the New Zealand conference and 10th overall, beating the Waratahs shapes as critical to the Chiefs' season.

Foster isn't pushing the panic button yet.

"Two close losses (Hurricanes and Blues) either side of two good wins over the Rebels and Sharks show we are playing reasonably well, but we have to improve closing out tight games in order to build the sort of momentum we are looking for," Foster said on Wednesday.

"From our perspective, we feel a little frustrated. We feel we have been doing a lot of good stuff and we know we still got a bit of growth to do.

"We've just got to be a little bit more clinical over 80 minutes."

Umaga and Taumalolo will be on the bench, where halfback Tawera Kerr-Barlow replaces Taniela Moa.

Chiefs: Tim Nanai-Williams, Lelia Masaga, Richard Kahui, Dwayne Sweeney, Sitiveni Sivivatu, Mike Delany, Brendon Leonard, Liam Messam (Capt), Tanerau Latimer, Scott Waldrom, Isaac Ross, Craig Clarke, Nathan White, Hika Elliot, Toby Smith. Reserves: Aled de Malmanche, Sona Taumalolo, Culum Retallick, Fritz Lee, Tawera Kerr-Barlow, Tana Umaga, Save Tokula.

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