The Red Sox signed the sinkerballer as a non-roster invitee, hoping he could resuscitate a career that has fallen on hard times in recent seasons. Perhaps that still might be possible, but Kolb will open the season in the Minors.
"This is one of those [things] that we spoke about earlier in camp, we're out of innings," Francona said. "We're leaving [for Japan] in a week. He understood. He's a professional ... but he needs to go pitch and pitch on consistent days, which he can't do the rest of the camp here. That's the program there."
Francona also informed position players Joe Thurston and Keith Ginter that they will not make the team, but he invited them to stay in Major League camp until the Red Sox depart for Tokyo on March 19.
Kolb saved 21 games for the Brewers in 2003 and 39 a year later, but injuries and ineffectiveness have troubled him since.
Kolb, who turns 33 on March 29, worked in four Grapefruit League games for the Red Sox, posting a 4.91 ERA.
"Sometimes when you come in as a non-roster guy, you're asked to compete before you're really ready to," Francona said. "It's still Spring Training and he's kind of a veteran guy, and we kind of explained that to him. We understand that. But I think he felt like his ball was starting to sink again and he just needs to command and get in that rhythm where he can go out and pitch every day, every other day, and we didn't see that happening the rest of camp, so that's why we have to make the move."
Now that Kolb is out of the picture, Bryan Corey, David Aardsma and Craig Hansen are among those contending for the last bullpen spot.
With the departure to Tokyo looming, the Red Sox will continue to pare down the roster over the next few days. Once the Thurston and Ginter moves are official, the Red Sox will have 43 players left on their Spring Training roster.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.