Thames has been optioned to Triple-A Norfolk, but he will report to Sarasota while rehabbing a non-displaced fracture of the second metacarpal of his left hand, suffered when he was spiked in a collision with an infielder on June 15 with Tacoma. He's expected to be cleared for baseball activities within the next 10 days.
Thames, 26, has appeared in 181 major league games for the Blue Jays and Mariners, batting .250/.296/.431 with 21 home runs and 62 RBIs. In 57 games with Triple-A Tacoma in 2013, Thames hit .295/.382/.479 with seven home runs and 33 RBIs.
Thames originally was drafted by the Blue Jays in the seventh round of the 2008 First-Year Player Draft out of Pepperdine University.
Kelly, 24, is a career .283/.380/.378 hitter in five seasons in the Orioles organization after being selected in the 13th round of the 2009 First-Year Player Draft out of the University of California-Davis.
The Orioles were interested in Thames last year before he moved from the Blue Jays to the Mariners organization. He's a career .261/.307/.446 hitter against right-handers, and .210/.257/.337 vs. left-handers.
"He's got some major league experience," said executive vice president Dan Duquette. "He's got a live bat. He hits for average and has power against right-handed pitching. We thought he'd be a good addition.
"He's young, he's got pretty good speed and a live bat."
The Norfolk outfield already is crowded with LJ Hoes, Xavier Avery, Jason Pridie and Henry Urrutia, but the Orioles will make room for Thames.
Thames homered onto Eutaw St. off Orioles right-hander Tommy Hunter in April 2012.