United, who trailed thanks to Kane Hemming's first goal, registered their first win of the season - and the first of the Chris Wilder era - thanks to second half goals from Billy Sharp and James Wilson.
And Blades assistant boss Knill, when asked what was said to United's players at half-time, revealed: "We told them they were playing well, and to keep going. We had great chances in the first half that we didn't take but if we kept believing, it would come.
"And then when it did... Wow. What a crowd and what a ground. Get that goal and the crowd were unreal and from then, there was only going to be one winner. "
Watch the the video above to hear Knill's thoughts on United's first win