The Brazilian has lit up Ligue 1 since leaving Barca for Paris Saint-Germain in August, becoming the world's most expensive player following the €222million deal.
But a broken foot ruled Neymar out of the second leg of a last-16 Champions League tie with Real Madrid, and the 26-year-old is also a doubt for the World Cup.
Reports have suggested Neymar is unsettled at PSG, with Madrid regularly linked to a move for the forward since he left La Liga.
But Valverde rejected speculation Neymar could make a sensational return to Barcelona after a single season with PSG.
"I don't know where that has come from," Valverde told reporters on Friday. "Let's not talk about hypothetical situations."
Valverde was also asked about Gremio midfielder Arthur, who is reportedly closing in on a €40m move to Camp Nou.
"Would he fit in? He plays for a different team, it would be absurd - we have a policy not to talk about players at other teams," Valverde said.
"To speak out of place would be taken out of context. He is a good player but he doesn't play for us, I'd rather speak about my own players."