The Argentina star is set to miss the next six weeks due to a hamstring injury, his third lay-off of the season already.
Messi has scored 14 goals in 16 outings under Gerardo Martino this term, having fired Barca to Liga glory last season, scoring 46 times in 32 games.
Valdes has backed Messi to bounce back from his disappointment, hinting Barca could struggle in his absence such is their dependance on him.
The goalkeeper said: "He is god, the best there is and he always will be, for what he has given to this team and what he has made me experience as his team-mate.
"For me, Barca will always depend on him because he is the best in the world.
"To me he seems sad. By defect we players are selfish and we can't understand it when we can't play.
"Knowing him and the winner he is I have no doubt what he will now put into recovering, in fact he is already doing so."
Messi posted a message on his official Facebook account, thanking his fans for their continued support as he aims to return to top condition.
He wrote: "As many people know in the next few weeks I will be full time trying to recover from this new injury.
"For me it is a shame that I can't play with my side at the moment. Now the most important thing is to recover well so I can help my team-mates and return all the support I have received in the way I know best, by playing football."
