"I would say the chances of Bobby pitching -- we're probably past that point now," said Francona. "He just couldn't get it going this weekend, and that was probably the cut-off point. We're going to let him get looked at and see what they decide to do."
Instead of traveling to Toronto, Jenks stayed back for an exam with back specialist Dr. Kirk Wood at Massachusetts General Hospital.
Jenks went on the disabled list three times this season, the first because of a right biceps strain and the last two times for left back tightness.
Complicating his recovery, Jenks twice got very ill, even being forced to the hospital during the first sickness.
"He got sick, then he got sore," said Francona. "It's just been one thing after another. When he got back, he wanted to try and take one more shot at it, and it just wasn't happening."
Signed to be one of the key pieces of Boston's bullpen, Jenks pitched just 19 games, going 2-2 with a 6.32 ERA. His last appearance was July 7. Jenks is also under contract for next season.
"We're not disappointed in him -- we're disappointed," Francona said. "The role we envisioned never came into fruition for various reasons all year, and so we tried to fill that role. At times, [Matt] Albers for the longest time just saved us, and [Alfredo] Aceves, almost in a different role. Those guys have picked up so much slack.
"But having a guy who can be reliable, that's been through it, can pitch the seventh, eighth or ninth, can pitch to lefties or righties, yeah, it's a big deal. But we haven't [had] it. It's not like we had two good months of it and now we've got to replace it."
Perhaps the best-case scenario for the Sox is if starting pitcher Clay Buchholz could recover in time from the stress fracture in his back to be a seventh-inning weapon by the postseason.
Buchholz started playing catch last week.
"Tomorrow, he'll start stretching it out a little bit," Francona said. "Start out with distance, then get to quantity."
There is no timetable for when Buchholz will throw off a mound.