Diaz, MacDonald face off in Toronto
Heavy.com confirmed the booking with a source close to the organization on Friday. MMAFighting.com first reported the news.
Diaz is coming off a loss to Dong Hyun Kim at UFC 125 earlier this month. It will be his fourth bout as a welterweight.
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MacDonald has not competed since losing to Carlos Condit at UFC 115 last June. That loss was the first of his pro career. MacDonald was scheduled to face off against Brian Foster at UFC 123, but an injury forced him to withdraw from the fight.