The young midfielder has yet to really break into the first team at the Camp Nou outfit, but has already attracted the interest of the Portuguese rivals
"I know that Benfica are interested, because they have come to see him live in action a few times. Although they have not contacted me yet," Diaz was quoted as saying by El Mundo Deportivo.
"Sporting [Lisbon] did approach me last month to discuss the possible conditions of a transfer this summer."
The 19-year-old midfielder joined the Barcelona youth academy from Espanyol in the summer of 2004 and made his official debut for the Champions League winners in the Spanish Super Cup in August 2010.
Romeu has a contract with the Catalan side until the summer of 2012.