Saarloos was 1-5 with a 7.17 ERA in 31 relief appearances and three starts with the Cincinnati Reds last season. He pitched previously with the A's, going 19-17 with a 4.42 ERA in 70 games from 2004-06.
Hernandez had been selected in the winter-meeting draft from the White Sox organization last December and went 1-0 with an 18.00 ERA in three appearances.
He won his major league debut in Toronto last Wednesday. But in his last two outings, he allowed six runs, four hits and three walks in two innings.