Okajima had been on the DL since Aug. 6 with a right hamstring strain. He tossed a 30-pitch bullpen session at the Tampa Bay Rays' Tropicana Field on Friday and suffered no setbacks. He's 4-3 with a 5.85 ERA this season, but has not been consistently effective.
Due to Okajima's recent hiatus, Red Sox manager Terry Francona hopes the southpaw will turn things around in the final five weeks of the season.
"It'll be a big lift. We've leaned on him for a couple of years," Francona said, "and he's been such a big weapon for us, that he'll be really welcomed."
Bowden tossed a side session at Tropicana Field on Saturday afternoon and left for Boston prior to Saturday night's game against the Rays. He'll rejoin the PawSox on Monday at McCoy Stadium.
The right-hander has had two stints with Boston this season as a reliever and has worked a total of six innings, allowing four runs on 10 hits with six strikeouts.
Joe McDonald covers the Red Sox for ESPNBoston.com.