Red Sox trade Wade Miley to Mariners for Carson Smith, Roenis Elias

Are the Red Sox done dealing? (2:45)

Jim Bowden and Jerry Crasnick break down Boston's acquisition of Carson Smith from the Mariners for Wade Miley and if Boston team president Dave Dombrowski is done dealing this offseason. (2:45)

NASHVILLE, Tenn. -- The Boston Red Sox have bolstered a suddenly imposing bullpen, acquiring right-hander Carson Smith and lefty Roenis Elias on Monday from the Seattle Mariners for left-hander Wade Miley and reliever Jonathan Aro in the first trade announced at the winter meetings.

Smith, 26, had an impressive first full season in the big leagues, going 2-5 with 13 saves and a 2.31 ERA in 70 appearances for Seattle. He will join the back end of a bullpen anchored by new closer Craig Kimbrel.

"I think it really gives us another power arm in the bullpen," Red Sox president of baseball operations Dave Dombrowski said. "It gives us a little more depth out there."

The Red Sox had one of the worst bullpens in baseball last year, as they finished last in the American League East. But Dombrowksi, in his first offseason running the Red Sox, has moved swiftly to improve the relief corps.

He acquired Kimbrel, an All-Star stopper, from San Diego less than a month ago and now has added the sidearming Smith to a group that includes Koji Uehara and Junichi Tazawa.

Dombrowski has said Uehara will be Kimbrel's setup man, but Smith should slot in right behind the former closer. Manager John Farrell is looking forward to having a more defined bullpen next season.

"What's clearly different with this group is that it's deeper in talent, it's deeper in performance, it's deeper in the ability to get strikeouts in key spots," Farrell said. "We've got the ability to now assign innings to individual guys where they can probably mentally prepare for that inning."

Smith has been very impressive in his brief big league career, compiling a 2.07 ERA in 79 appearances. He has 92 strikeouts in 70 innings.

"When you consider the arm slot of Smith in addition to the wipeout type of slider and power fastball, he's really the unique one in the group," Farrell said.

The Red Sox were willing to part with the dependable Miley after signing ace lefty David Price to a $217 million, seven-year contract.

Acquired from Arizona during the week of last year's winter meetings, the 29-year-old Miley was 11-11 with a 4.46 ERA in his only season with the Red Sox and is 49-46 in five big league seasons. He is owed $6 million next year and $8.75 million in 2017 as part of a $19.25 million, three-year contract that includes a $12 million club option for 2018 with a $500,000 buyout.

He had been slated as the fourth starter in a rotation with Price, Clay Buchholz and Rick Porcello. Instead, Miley will take the rotation spot in Seattle that opened with the loss of free agent Hisashi Iwakuma, who agreed to a contract with the Los Angeles Dodgers late Sunday, a source told ESPN.

"We just weren't willing to go to the third year," on Iwakuma, Mariners general manager Jerry Dipoto said. "We went as far as we were willing to go."

The Japanese right-hander has been injury-prone in his first four big league seasons, never reaching 180 innings. Miley is durable, exceeding 190 innings in each of his four full years.

Miley has a long history with Dipoto, who was scouting director for the Arizona Diamondbacks when Miley was drafted in 2008.

"Wade provides stability to the rotation," Dipoto said. "He's a great competitor."

Aro, a 25-year-old right-hander, made his big league debut in June and had a 6.97 ERA in six relief appearances with the Red Sox.

Elias, a 27-year-old left-hander, was 5-8 with a 4.14 ERA in 20 starts and two relief appearances.

Dombrowski said the Red Sox would consider using Elias out of the bullpen, but his inclusion in the deal potentially provides more depth for the rotation.

"He'd have to win the job in spring training," Dombrowski. "We do like his arm."

The Associated Press and ESPN's Buster Olney contributed to this report.