Manager John Gibbons says Navarro is expected to miss several days as he deals with a family matter.
Gibbons says Wagner was called up to help out at the back of Toronto's bullpen with closer Casey Janssen and setup man Steve Delabar both unavailable Wednesday.
Wagner had three saves in five games at Buffalo. He has pitched in nine games for Toronto, going 0-0 with a 3.12 ERA.
Kratz has played in 11 games for the Blue Jays, batting .231 with two homers and six RBIs.