All Blacks legend Dan Carter stumbled upon the video, retweeting it with the caption: "Don't know how I missed this. This made my day. Teach them young".
Since being shared by Carter, the video has racked up more than 720,500 views and 36,000 likes.
"My heart just about exploded. Kia kaha, kia manawanui little one," one Twitter user commented.
"Absolutely world class that's what you call a cheer everyone up video classic," wrote another.
Wainui scored a try late in the second half for the Chiefs in their match against the Crusaders on Sunday in Christchurch - which the Chiefs ultimately lost 18-13.