In return, the Mariners would receive Cuban pitching prospect Ariel Miranda, according to multiple reports. The deal is pending physicals.
Miley, who was acquired by the Mariners in an offseason trade with the Boston Red Sox, has struggled this year with a 7-8 record and 4.98 ERA, but had one of his best outings of the year Saturday against the Chicago Cubs. Miley, 29, threw six no-hit innings and struck out nine in a 4-1 win at Wrigley.
Baltimore, which leads Toronto by just a half-game in the American League East, has been in the market for a starter, particularly a lefty, as it looks to help its postseason cause.
The deal was first reported by FanRag Sports and confirmed by ESPN.