Bielak is recovered from right shoulder surgery and will participate in Tread Athletics' Pro Day in January, Ari Alexander of WHDH 7News in Boston reports.
Bielak signed a minor-league contract with the Diamondbacks in February, but he was released after making just two appearances at Triple-A Reno following shoulder surgery. It's not clear what the exact nature of the procedure was, but Alexander says Bielak has resumed throwing bullpen sessions. The 29-year-old holds a career 4.63 ERA over 76 appearances (21 starts) at the major-league level.