"There's no changes to the roster as of this moment. The reason he's here, as part of the taxi squad that we're allowed for a day, provided by MLB," Farrell said.
Because it's been fewer than 10 days since Castillo was optioned to the PawSox, the only way he can be added to the roster is in the event of a player going on the disabled list. Farrell said that if Ramirez had experienced a setback Tuesday, Castillo would've been available to take his place.
"Hanley has had a good day so far. He'll take regular BP today, he swung in the cage," Farrell said. "He's making pretty solid progress over the last 24 hours."
Farrell was hopeful ahead of the series opener on Monday that Ramirez, who's day to day with a bruised left hand, would be able to return at some point during the team's four games in Toronto. That hadn't changed Tuesday.
Ramirez hasn't played since Wednesday, when he was hit in the hand with a line drive while running the bases. Alejandro De Aza has slotted into left field in Ramirez's absence. He made a key running catch on a Jose Bautista fly ball to save a run in the sixth inning on Monday while going 3-for-4 at the plate.
De Aza was back in left for the sixth game in a row on Tuesday. He has gone 9-for-21 with three homers and six RBIs since taking over for Ramirez.
Farrell said once Ramirez is ready to go, he could see De Aza moving to right field in a platoon role with Shane Victorino, who's on the DL with a left calf staring but could be activated at some point during the club's upcoming homestand.
Jamie Ross is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.