Neymar arrived at the Nou Camp on June 3, signing a five-year contract for 57million euros from Santos, but Cruyff believes the 21-year-old Brazilian forward will struggle to work alongside Argentinian Messi in Tito Vilanova's frontline.
Cruyff told Marca: "With Neymar signed, I would have planned for the possibility of selling Messi. Some would agree with that, others not.
"You are talking about a team, its players, the things around it... There are too many things at stake. That's why it's so difficult to manage such a top-class squad."
Cruyff believes it will be difficult to satisfy two prodigious talents like Messi and Neymar on the same pitch, and that problems could also occur due to the two players having contracts with different sponsorship arrangements.
"It's like the free-kicks. Neymar is very good at taking them, and Messi has already shown he is. Who's going to take them?" he said.
"Or the fact that Neymar and Barcelona are with Nike while Leo is with Adidas. These are situations that could cause problems."