Wales have conceded 248 points and 34 tries in Tandy’s five games in charge so far with no specialist defence coach in place.
Tandy combines the head coach job with the defence position, the specialist role that he had successfully held with Scotland and the British and Irish Lions.
Pundits such as former Wales wing Alex Cuthbert and ex-Scotland captain John Barclay have questioned whether Tandy can do both roles.
But Sherratt said the arrangement will continue.
“He is a very good defence coach, he is the British Lions defence coach and it’s not one thing [causing the problems],” he said.
As the attack coach, Sherratt comes up against France defence coach and former Wales favourite Shaun Edwards this weekend.
“I know Shaun well, I worked with him with Wales, Cardiff and the Ospreys and he’s a world-class coach,” said Sherratt.
“It’s more about the players going against their defence rather than me against Shaun because, on and off the pitch, he’s pretty formidable.”
