The right-hander has been dealing with numbness in the pinkie and ring finger of his right hand and was originally supposed to pitch on Saturday in Toronto.
"We're not going to pitch him until he's symptom-free," said Francona. "We wouldn't do that. "That's kind of where we're at. We're not hiding an aneurysm or a ... clot."
Francona was somewhat taken aback by a story by The Associated Press that stated the Red Sox would test Beckett to make sure he doesn't have a blood clot.
From what the training staff has told Francona, no such tests are necessary. Apparently, the problem has been brought on by Beckett sleeping on top of his arm.
"[Assistant trainer] Mikey [Reinold] and those guys have done a lot of homework on why," Francona said. "Through doing some homework, they kind of came to the conclusion that this had been what was happening, to the point where I think we got a lot more comfortable with the explanation, but still, at the same time, we're not going to pitch him until he's symptom-free."
Beckett felt much better on Wednesday, to the point that he tried to lobby the training staff into letting him resume his throwing program two days earlier than scheduled.
"He's begging today, and Mikey said no," Francona said. "He's begging for tomorrow. Mikey is still saying no. Friday, Mikey is OK with. I wouldn't be surprised if Beckett wins part of this and [Reinold] says yes to tomorrow. I guess the point is, if Beckett really wanted to throw, that's always a real good sign."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.