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 in 19 starts, 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.
Drafted by Arizona in the first round of the 2008 draft, Miley set Diamondbacks rookie records for wins (16), starts (29) and innings pitched (194.2 IP) in 2012 en route to his only All-Star Game appearance.
His ERA has increased every season since, but he has started at least 32 games over the past four seasons.
Miranda is 4-7 with a 3.93 ERA in 19 starts for Triple-A Norfolk this year. The 27-year-old southpaw made one appearance for the Orioles, surrendering three runs on four hits while striking out four over two innings against Seattle on July 3.
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 the Orioles look to bolster their rotation and help their postseason cause.
The deal was first reported by FanRag Sports.