According to a source close to Smoltz, the 41-year-old right-hander plans on calling the Braves -- the only team he's ever pitched for -- on Thursday morning and telling them that he has decided to play for the Red Sox.
Smoltz is coming off extensive shoulder surgery, which limited him to just six appearances in 2008.
The Red Sox, who have a deep rotation, are expected to take a conservative approach to Smoltz's rehab, one in which the righty could debut for them around June 1. Boston took a similar path with Bartolo Colon in 2008, but the big righty never could stay healthy for a prolonged period.
The deal Smoltz appears set to sign with the Red Sox is for $5.5 million over one season, with attainable incentives that could bring it as high as $10 million.
Once Smoltz is ready to pitch, he will join a talented rotation that includes Josh Beckett, Jon Lester, Daisuke Matsuzaka, Tim Wakefield and perhaps Brad Penny, who is expected to officially sign with the Boston in the coming days.
All along, there was some skepticism of whether Smoltz would leave Atlanta, the team he broke in with way back in 1988. But negotiations apparently never progressed to the point with the Braves this winter where Smoltz felt compelled to return.
He has a career record of 210-147 with a 3.26 ERA and 3,011 strikeouts.
Smoltz was converted to the closer's role from 2001-04, where he was also dominant, posting 154 saves.
Though Smoltz has had his share of arm injuries through the years, this past season was the first time since 2000 that he made fewer than 30 appearances. As recently as 2007, Smoltz was still pitching at a high level, going 14-8 with a 3.11 ERA and 197 strikeouts. The Red Sox's main wish for Smoltz is that he will be healthy and thriving during crunch time.
Smoltz has a postseason track record (15-4, 2.65 ERA) similar to former Sox veteran Curt Schilling. He pitched in five World Series, including Atlanta's championship edition of 1995.
Smoltz was the National League's Cy Young Award winner in 1996, when he went 24-8. He is an eight-time All-Star.
Ian Browne is a reporter for MLB.com. Mark Bowman, a reporter for MLB.com, contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.