He hit .295 with seven home runs and 33 RBIs in 57 games for the Rainiers after batting .220 with six homers and 14 RBIs for the Mariners last year. In 181 Major League games, Thames has hit .250 with 21 home runs and 62 RBIs.
Kelly, 24, was hitting .283 with one home run and 47 RBIs in 72 games for the Orioles' Double-A Bowie team. He will report to Tacoma for his first Triple-A stint after batting .283 in five seasons in the Minors.
Kelly ranks second in the Eastern League in runs (51) and doubles (21), is third in walks with 51 and has hit .337 during a 27-game stretch since May 29. Originally selected by the Orioles in the 13th round of the 2009 Draft out of the University of California, Kelly led all Orioles' farmhands last year in hits (154) and total bases (220).
The Orioles optioned Thames to Triple-A Norfolk. He is currently sidelined with a broken bone in his left hand. He was designated for assignment on June 22 when the Mariners needed a 40-man roster spot to activate Franklin Gutierrez from the 60-day disabled list.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.