Aerosmith played to thousands of screaming fans during the second night of 2013's Monsters of Rock Festival in Sao Paulo, Brazil, on Oct. 20, but bassist Tom Hamilton was not in attendance.

Blabbermouth reports that Hamilton was forced to bow out of the show after taking ill. Details aren't available, but it's worth noting that Hamilton has needed some time off from the band's tours a number of times in recent years, including their spring 2013 trip to Australia. Here's hoping Hamilton's latest health woes aren't connected to his battle with cancer, which has seen him undergo experimental surgery.

Aerosmith fans at the Monsters of Rock show could at least take comfort in knowing that the band has a capable replacement: David Hull, the former Joe Perry Project member who's stepped in for Hamilton on a number of occasions in the past.

Hull, who traveled to Australia with the group in the spring, is also a recording artist in his own right -- perhaps most notably in the mid-'80s, when he briefly changed his last name to Heit and teamed up with fellow Perry Project vet Charlie Farren to create the short-lived band Farrenheit.