He was placed on the bereavement list Tuesday after the death of his grandmother-in-law.
Alvarez is batting .234 with 15 home runs, but recently has been relegated to bench duty because of throwing problems. Alvarez leads all major leaguers with 23 throwing errors.
To make room for Alvarez on the 25-man roster, RHP Ernesto Frieri was designated for assignment.
Frieri was acquired by the Pirates on June 27 in exchange for former closer Jason Grilli. Frieri had a 10.13 ERA in 14 appearances with Pittsburgh.