The experienced centre-half has been training with Wolves in pre-season after leaving Celtic and he played in Saturday's 2-0 defeat by Bristol City.
Balde also faced Walsall in a friendly earlier in the week, but is short on match fitness after making just four SPL appearances for Celtic last term.
McCarthy is not ruling out a deal for the 33-year-old, but believes Balde needs time to show he is up to playing in the Premier League.
"A decision may be a while because Bobo isn't fit enough yet - he hasn't played for a long time," McCarthy told the club's official website.
"By his own admission he's not fully fit yet and I was tempted not to play him because he ran himself to exhaustion on Tuesday night.
"I wondered about playing him, but at the same time he needs to get some time on the pitch.
"It may be a while before a decision, but he wants that too because he wants to show us what he can do when he's fully fit."