He anchored the Canadian 4 × 100 m relay team to a third-place finish at the 2012 Summer Olympics, but they were later disqualified for a teammate stepping out his lane.

A year later on August 16, 2006, he claimed the silver medal in the 100 m at the 2006 World Junior Championships in Athletics,[7] held in Beijing, China, in a time of 10.39.

Warner received a full scholarship to Texas Christian University where he competed in the NCAA as a Horned Frog under Darryl Anderson.

In the final, the Canadian relay team arrived in third place and initially believed they had won bronze but they were disqualified when officials judged that Connaughton had stepped on the lane line just before passing the baton.

[8] In August 2013 Warner anchored his Canadian teammates Gavin Smellie, Aaron Brown and Dontae Richards-Kwok to a bronze in the same men's sprint relay event at the 2013 World Championships in Athletics in Moscow, after Great Britain was disqualified for a baton exchange infraction.