Wasps have now failed to win any of their opening four games, and McGeechan admitted: "We were awful and that's the worst performance of the season.
"It could have been a lot more than 16-0 and I thought we defended well.
"We were very poor with the ball and very poor without it.
"We've got to front up now, as players and as coaches."
Three defeats and a draws marks the club's worst-ever start to a Premiership season and even allowing for the absence of a host of key men due to World Cup commitments, McGeechan had every right to be alarmed by his side's performance.
Head coach Shaun Edwards said he could not remember Wasps being nilled since a Heineken Cup game against Stade Francais in 2001.
An ashen-faced McGeechan added: "We didn't respect the ball; it's as simple as that. Sale were the better side and thoroughly deserved their victory."
Sale fly-half Charlie Hodgson orchestrated Wasps' demise with a masterful display which harvested 11 points.
Hodgson, playing only his fourth competitive game for Sale since injuring his right knee playing for England against South Africa last November, displayed courage as well as no little skill.
He was heavily winded by a thumping challenge from Wasps forward Dan Leo in the opening exchanges but he gingerly rose to his feet to dominate affairs.
Two first-half drop-goals a penalty from the No 10 gave Sale a 9-0 interval advantage which they did not surrender.
Magnus Lund squeezed over for the game's only try in the 53rd minute and with Hodgson adding an excellent touchline conversion, the visitors were dead and buried.
Sale director of rugby Phillipe Saint-Andre pointed an accusing finger at the officials after his side had several tries ruled out.
"We should have had a bonus point but we were in control for the the eight minutes," said Saint-Andre.
"We worked so hard in the forwards and we created a lot as well.
"It was a very good team performance. Charlie got winded early on but we again showed signs that he is getting back to his best."