Ranaudo takes the rotation spot of Miguel Gonzalez, who was placed on the 15-day disabled list with a groin strain last week.
The right-handed Ranaudo made one previous start with the Sox this year and showed well, allowing three earned runs on two hits over 6.2 innings against the Cubs on July 27. At Triple-A Charlotte, he is 6-5 with a 3.35 ERA in 16 starts.
He will pitch on regular rest Wednesday.
In a little bit of a surprise, Carson Fulmer was optioned to Triple-A Charlotte to make room for Ranaudo on the 25-man roster.
Fulmer, the No. 8 overall pick in the 2015 draft, was used strangely and sparingly since his July 15 promotion. He appeared in just eight games and posted an 8.49 ERA in 11.2 innings of sporadic work.
That's the equivalent of about two starts in a month, so it's hard to say how much this one month in the big leagues helped Fulmer's development.
He never pitched on back-to-back days, and he only pitched on one day's rest twice. Basically, he was collecting rust in the bullpen. During the same period where Fulmer made eight appearances, Matt Albers pitched 11 times, which is strange because there's no upside to giving more opportunities to a veteran retread such as Albers.
Reports indicate Fulmer will be "stretched out" at Triple-A Charlotte for a potential start or two in September after roster expand. I'm fine with that. I don't care whether Fulmer is at Triple-A or the big league level. I don't care whether he's starting or relieving. I just want him getting opportunities to pitch and refine his craft.
Getting on the mound more frequently can only help him. Rotting on the bullpen bench with a bad team doesn't do anything for his development.