Rapada was traded for a player to be named or cash considerations. Most likely, that return will be known after the Rule 5 Draft later this week.
Thomas, who last pitched in the Majors with the Twins in 2004, returns to the states after pitching most of the past four seasons in the Far East. The 32-year-old went 5-11 with 44 saves and a 2.86 ERA over the past two seasons combined for Hanwha of the Korean Baseball Organization. He struck out 119 batters over 113 1/3 innings.
Before arm injuries, the Australian native was a top pitching prospect for the Twins and a participant in the 2001 All-Star Futures Game, where he put a mid-90s fastball on display. He pitched just 11 games over three seasons with the Twins, however, and after a trade to the Red Sox decided to take his game closer to home.
He pitched two years with the Nippon Ham Fighters in Japan, going 5-6 with a 4.21 ERA and 94 strikeouts over 94 innings, before heading back to the United States for another try on a Minor League deal with the Mariners. He went 8-6 with 4.87 ERA as a swingman at Triple-A Tacoma, allowing 138 hits over 116 1/3 innings, before heading to Korea.
His performance there, as well as his brief stint with the Aussies in this past season's World Baseball Classic, convinced Detroit international scouting director Tom Moore to take a look and the Tigers to take a shot. Dombrowski said the Tigers' scouting and video clocked Thomas' fastball at 92-95 mph.
"He's a guy that we tried to sign very hard," Dombrowski said. "He was a quality prospect in Minnesota years ago, pitched in Korea the last couple years. We were getting a lot of competition from Japan, but our guys had watched him pitch and were on top of that situation."
Exactly where he fits into the Tigers' situation isn't certain. Fu-Te Ni's emergence in Detroit alongside Bobby Seay essentially ensured Rapada wasn't leaving the Mud Hens, for whom he went 4-2 with a 2.76 ERA and five saves while striking out 47 batters over 45 2/3 innings.
Now with Thomas, the Tigers have the potential for three lefty relievers in a seven-man bullpen, or the depth to make a move if they so choose. Bobby Seay is a year away from free agency.
Thomas agreed to a Major League contract, meaning he goes immediately on the 40-man roster and takes Rapada's place. Detroit also outrighted right-hander Zach Simons to Triple-A Toledo. Simons, acquired two years ago from Colorado for Jason Grilli, went 4-2 with a 2.73 ERA in 42 outings between Double-A Erie and the Mud Hens.
Simons' roster spot went to free agent Adam Everett, who returned to the Tigers on a one-year deal later in the day.
Rapada, a Tiger for parts of the past three years after coming over from the Cubs for Craig Monroe in 2007, will get a fresh start in his third organization after seeing rare time in Detroit over the last year and a half.
The 28-year-old sidearmer pitched in just three games for the Tigers -- two early in the year, then another as a late-season callup. He was originally left out of September callups until injuries left Detroit needing another arm in the bullpen.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.