Should the 20-year-old impress, a place in Vicente del Bosque's squad could arrive for the competition in Brazil.
"I'd finished my spell at Everton and I was on my holidays. I got a call from Andoni Zubizarreta (Barcelona's sporting director), who told me I had the chance of a call and very quickly, I started training again and I'm really happy," Inside Spanish Football quotes the youngster as saying at a press conference.
"It's been great from all the players. I'm really happy to be here, working with these players. I'm really happy how they've all welcomed me, those who I know from Barcelona, as well as everyone else. I'm really happy.
"I'm not thinking about Brazil, I just have to enjoy this week. I want to learn from them all and whatever happens, will happen. [Jesus] Navas is injured, so I'm taking his place this week. It might push me a little closer, but I don't want to think about Brazil just yet. I have to repeat, all I want to do is learn."
Deulofeu has made 13 appearances for Spain's Under-21 outfit.