The Red Sox optioned Kelly to Triple-A Worcester on Thursday, Chris Cotillo of MassLive.com reports.
Kelly had been solid out of the bullpen for Boston with a 3.31 ERA, 1.29 WHIP and a 14:7 K:BB through 17 appearances. The demotion is a mild surprise given that the right-hander had been great in his last 12 games with a 1.64 ERA and 11 strikeouts. He seems likely to get another look in the majors later this season.