Bradley had struggled of late. Between July 26 and Aug. 12, he was 0 for 35. His batting average over the past four weeks is .179.
Betts was ranked the No. 62 prospect in baseball prior to the season. This will be his third stint in the big leagues this season.
The 21-year-old played 10 games with Boston in late-June and July, and he was also with the team in August before being sent down to make room on the roster for Kelly Johnson.
Betts has batted .244 in 44 major-league at-bats. He split time between Triple-A Pawtucket and Double-A Portland this season, batting .346. He can play second base, shortstop, centerfield and rightfield.
- Dan Gartland