Melbourne Victory media bossTrent Jacobs told au.fourfourtwo.com that the club doesn't know the exact nature of the illness but will give the player the time he needs.

"We don't believe the illness is related to this swine flu situation. But his son has fallen very ill, but  we just don't know the exact nature of the illness," he said. "We just don't know."

Meanwhile, there is increasing confidence at the A-League champions that a big-money deal to buy the player from Costa Rican club LD Alajuelense will go through.

Hernandez returned to Australia last week to begin preparations for the new A-League season as negotiations to re-sign him ramped up.

The exciting Tico has also been linked with a move to the MLS in recent months.

"He's obviously a very key player for us in our championship defence and negotiations are ongoing, but also advanced a lot further than in the last couple of weeks," added Jacobs.

"There is no announcement right now [on the transfer], but it's getting closer."