The Portland Sea Dogs officially added Justin Masterson to the rotation, scheduling him to pitch Friday night at Hadlock Field. The Sea Dogs are playing the Bowie Baysox at 7 p.m.

Masterson, a Red Sox starting pitcher at the start of the season, is on the disabled list with a tired arm. He was 2-2 with a 6.37 ERA before going on the DL on May 14.

Pitcher Justin Masterson signed a $9.5 million, one-year deal with the Red Sox in December. The Associated Press

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This will be Masterson’s second rehab start. He pitched for Pawtucket last Sunday, but did not last two innings. Boston manager John Farrell indicated that Masterson would next pitch at Portland, but it was not official until Thursday.

Masterson, 30, is making his first appearance at Hadlock since he pitched for the Portland Sea Dogs in 2007 and ’08.