From mlb.com:
INF Christian Arroyo (left hamstring strain)
Expected return: Aug. 20
Arroyo has had a good rehab week and ran the bases again on Aug. 15. The plan is for him to start a Minor League rehab assignment on Aug. 17. If all goes well, Arroyo could be activated for the Aug. 20 game against the Rangers. Arroyo’s right-handed bat would give manager Alex Cora more flexibility against lefty starters. He is also a good pinch-hitting option against lefties. (Last updated: Aug. 15)
LHP Darwinzon Hernandez (right oblique strain)
Expected return: September
It has been slow going for Hernandez in his return from a right oblique strain, and it now looks as if he won’t return until September. The move of Martín Pérez to the bullpen has helped fill the void left by Hernandez. But getting Hernandez back for the stretch run could make a difference for the Red Sox.
“It's slow a little bit,” Red Sox manager Alex Cora said on Aug 15. “He played catch to 80 feet, he'll do the same thing today. I don't expect him to start a rehab assignment soon. He's not behind. He's where he should be with his process, so little by little he's getting better, but nothing off the mound for a while.” (Last updated: Aug. 15)
RHP Matt Andriese (right hamstring tendinitis)
Expected return: Aug. 17-18
Andriese will make the third appearance of his Minor League rehab assignment on Saturday for Triple-A Worcester. The Red Sox will reassess where he’s at on Monday and there’s a chance he could be activated for the series at New York on Tuesday. (Last updated: Aug. 14)
1B/OF Danny Santana (left groin strain)
Expected return: Aug. 20-24
Santana is on a similar timetable to Christian Arroyo and could go on a rehab assignment by Aug. 17. (Last updated: Aug. 13)
60-day IL
RHP Ryan Brasier (concussion)
Expected return: Late August
Brasier’s second appearance of his rehab assignment didn’t go nearly as well as the first. Pitching for Triple-A Worcester on Aug. 13, the righty allowed five hits and five runs. However, Red Sox manager Alex Cora didn’t sound concerned.
“I think the stuff was the same," Cora said. "I think he threw 18 pitches and they swung at 15 of them, so that’s part of the process. That’s part of rehab assignments. The stuff, the numbers that we got, they’re good. We’re still on the same path.” Cora added that Brasier will pitch again for Worcester on Aug. 15. (Last updated: Aug. 14)