Giles, who made $9 million last season, is a Type B free agent. By not offering Giles salary arbitration, a team that signs Giles won't have to surrender a supplemental pick between the first and second rounds of the 2010 First-Year Player Draft.
Giles, who will be 39 next month, hit .191 in 61 games in an injury-plagued season.
Giles, a career .291 hitter, spent parts of seven seasons with the Padres, hitting .279. He has said this offseason that he hopes to play in 2010.
Blanco, 38, threw out 40 percent of would-be basestealers last season and hit .235 in 67 games. He has already drawn interest from several teams, including the White Sox and Mets.
The Padres have also expressed interest in re-signing him to back up Nick Hundley.
Clubs have until 8:59 p.m. PT Tuesday to offer salary arbitration to their own free agents, and the players have until Dec. 7 to accept or decline.
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.