"He's still quarantined," Farrell said. "He will not [travel] with the team. He will travel on his own to the West Coast, but he's still in that phase where we have to keep him away from others, just from being so contagious."
Since being acquired from the D-backs on July 9, Ziegler has a 1.89 ERA with 21 strikeouts and just four earned runs in 19 innings.
"We're hopeful that he's in Oakland by Friday. That's the tentative plan," Farrell said. "This is something that came on Monday. This isn't your flu-like symptoms. It's type-A influenza. So we're keeping him away from everyone else."
Deesha Thosar is a reporter for MLB.com based in Boston. This story was not subject to the approval of Major League Baseball or its clubs.