In 16 starts this season, Porcello is 4-9 with a 6.08 ERA. In his last eight starts, the right-hander is 0-7 with an 8.18 ERA.
"Didn't want him to go 2 1/2 to three weeks without being in a game situation," said Farrell. "That will put Justin Masterson in the bullpen starting on Tuesday for the remainder of this homestand. That's where we are."
Ultimately, Farrell decided there was more of a benefit to letting Porcello try to end the half on a good note than shying away from him.
"He's a strong competitor," Farrell said. "He fully realizes the stretch he's in and what we're trying to do to get him to be consistent with his two-seamer and his curveball approach. You can throw all the bullpen [sessions] you want, and his bullpens have been quality. But it's the in-game execution where that's got to continue to be put forth."
Porcello's slump started not long after catcher Ryan Hanigan went on the disabled list. The righty has had a hard time getting into a rhythm with Blake Swihart and Sandy Leon.
"To match him up with [catcher Ryan Hanigan] is the approach being taken. We're doing everything that we can that's available to us to get him on the right track," said Farrell.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.