For Baster it was his 13th win at the highest level and his first since Ferlax won the Australian Guineas at Flemington in 2013.
Malaguerra has justified jockey's Ben Melham unwavering faith with a heart- stopping win in the group one Darley Classic later on the programme.
In a three-way finish, Malaguerra ($9.50) held off emerging Sydney sprinter Spieth ($8.50) with Fell Swoop close-up in the minor placing.
"I was very confident coming to this race today. As confident as you can be in a group one," the Victorian said.
Melham filled in for Luke Nolen when Black Caviar won the Melbourne Cup Carnival's major sprint in 2010 - the first group one triumph of the mare's unbeaten career. It was Melham's second group one sprint win during the spring carnival.