The Pramac d'Antin Ducati rider unintentionally held up factory Ducati rider Loris Capirossi by riding slowly on the racing line during Saturday afternoon's one hour shootout.
The Italian was visibly unhappy at the time, but Barros apologised and his former Honda Pons team-mate Capirossi - himself a veteran of 265 grands prix - later shrugged off the incident.
"I want to apologise to Loris for inadvertently slowing him while he was on his fast lap and costing him valuable positions," said Alex, who qualified 12th.
"That kind of thing happens, so no problem," stated eighth place Capirossi.