The Red Sox signed Kahnle to a minor-league contract Monday.
Kahnle was DFA'd by Boston earlier this month and elected free agency July 6. After testing the market, Kahnle has returned to the Red Sox on a minor-league pact and will join Triple-A Worcester. The 36-year-old pitched in eight games out of the bullpen for Boston last month and allowed eight runs on 12 hits and six walks with five strikeouts across nine innings.