Flick, who was previously Germany manager, said he had contacted Spain coach Luis de la Fuente by text message but there was room for improvement in their communication.
"I was also on this side, as a national team coach. I know how hard sometimes the job is," added Flick.
"I never spoke - I have had one conversation via text but I never spoke with him. My Spanish is not good, his English is not good, so maybe this is a problem.
"But in the end I think the communication - because we have not only one player there, we have many players there - it could be better."
Barcelona will host Valencia at their 6,000-capacity Johan Cruyff training ground as redevelopment work at the Nou Camp has not been completed.
The La Liga champions have been playing at Olympic Stadium in Montjuic for the past two seasons.
[Barcelona have said, external](https://www.fcbarcelona.com/en/club/news/4359784/fc-barcelona-statement) they are "working intensively to obtain the necessary administrative permits for the opening" of the Nou Camp "in the coming weeks", but a reopening date has not been confirmed.
"I spoke with the players, the captains, and they said it will not affect us," said Flick.
"When we play at the new Camp Nou, 105,000 \[capacity\], maybe it's a little bit different to playing at the Johan.
"As I said before it's not an excuse, I will not use it - Valencia also has to play in this stadium."