It was the Gulls third defeat on the spin and they sit just a point above the relegation zone after first-half goals from Ade Azeez and Krystian Pearce ultimately counted for nothing.
Pearce, making his first appearance since he was hospitalised with breathing problems last month, was outmuscled by former Gull Jo Kuffour for the first Wycombe goal and Knill criticised his side's defending.
"All we said was in the second half play forward, play in their half and for seven minutes we didn't do that," he said.
"We didn't do what we did in the first half. If you give them space to play in they will.
"If you compact that space they can't. We did that first half and played down the sides of them and for the start of the second half we just played backwards.
"All we wanted to do was make them defend, not us. So it's really tough to take.
"You score two away from home you should be winning the game, definitely not losing, and yet we concede three again for the second week in a row.
"He shouldn't have got in there for their first goal. We didn't react to it.
"We weren't good enough and I can make excuses that we're missing some players but it's pretty basic stuff."