The Red Sox released Kelly (elbow) on Friday, Chris Cotillo of MassLive.com reports.
The right-hander was designated for assignment by Boston on Monday and will hit the open market after passing through waivers unclaimed. Kelly had a 3.31 ERA, 1.29 WHIP and 14:7 K:BB across 16.1 innings this year for the Red Sox but spent the final three months of the season on the IL due to elbow inflammation.