Following a three-game series against the Blue Jays this weekend at Fenway Park, the Red Sox have three days off over an eight-day span from June 6-13.
The scheduling offers Farrell the opportunity to carry four starters while adding an arm to the bullpen. When Kelly was optioned, the Red Sox recalled reliever Noe Ramirez.
"The way the schedule lines out, if we were to stay with a fifth guy, we'd be looking at David Price on seven days' [rest] and I think once you get to that seventh day, starters start to get in that area where they'd much rather sign up for a fifth day. So we've got that ability to do that."
Only three pitchers remain from Boston's fluid rotation from a week ago -- Price, Rick Porcello and Steven Wright. In the seven days since, Clay Buchholz has been sent to the bullpen, Eduardo Rodriguez has made his season debut and Kelly has been optioned.
Farrell said that he had no issue with the four-man rotation including Rodriguez, who began the year on the disabled list with a broken right kneecap.
"We're only talking maybe three times through [the rotation]," Farrell said. "It's not like we're looking at this over the course of three or four months, so that's the approach right now."