The team on Wednesday also added minor league reliever Jesus Sanchez to their 40-man roster.
Hernandez went 3-0 with no saves in 26 relief appearances this year with Milwaukee, where he had a 7.68 ERA. The Brewers acquired him in June after Atlanta designated him for assignment. His career record is 178-177.
The Brewers acquired Torrealba in late September from Toronto for cash considerations. The 34-year old came to Milwaukee batting .233 with four homers and 14 RBIs. He was hitless in five at-bats for the Brewers.