Carlos is contracted to Corinthians, who have loaned him to second tier Oeste in a bid to gain regular first-team football.
With rumoured interest from Premier League giants, however, Guerra admitted that his club have no control over Carlos' contract, and admitted that the lure of European football may prove a temptation for the young defender.
"The player is under contract with us until the end of the Second Division," Guerra told Globo Esporte.
"But he is still a Corinthians player, so Corinthians have all the power in negotiations.
"When their board decide to have the player back he will have to return, be it to play for Corinthians or to negotiate with another club."
Carlos, whose full name is Antonio Carlos Cunha Capocasali Junior, joined Corinthians from Audax Sao Paulo in 2012.