The 30-year-old was sent for an X-ray, which revealed the fracture. Surgery will be required to fix an "evulsion of the extensor tendon," according to a Blue Jays spokesman.
"That's how life goes sometimes," Cabrera said through an interpreter after Toronto's 9-8 loss to Boston. "I wanted to finish strong, continue to help the team try to go to the playoffs."
It wasn't immediately known what time frame Cabrera faces in his recovery.
The loss is yet another blow to a lineup that is already without the services of infielder Brett Lawrie for the rest of the season. Losing Cabrera is even more severe considering he had been one of the Blue Jays' most valuable players all year.
Cabrera likely will receive consideration for the Comeback Player of the Year Award as he finishes with a .301 average, 16 homers and 73 RBIs in 139 games. Now the biggest question is whether Cabrera has played his final game in a Blue Jays uniform.
The Dominican native is set to hit free agency at the end of the season. He's likely all but guaranteed of receiving a qualifying offer and should be one of general manager Alex Anthopoulos' top priorities this winter. That doesn't mean his return is certain, but for now, Cabrera is saying all of the right things.
"I love the city of Toronto, I have great teammates, a great club," Cabrera said. "This was the club that gave me the opportunity after I got in trouble a few years ago [with a 50-game PED suspension] and I want to stay."
Toronto's chances of reaching the postseason have faded, but if the club wants to remain a potential contender, it can't dwell on Cabrera's injury for very long. One likely solution would see the return of Colby Rasmus into the starting lineup.
Rasmus lost his starting job in center field last week as Toronto made the decision to go with a platoon of Anthony Gose and Kevin Pillar in center. Rasmus could become part of a platoon in either left or center while recently acquired John Mayberry Jr. also could receive some consideration.
"That's one of our top dogs," Blue Jays manager John Gibbons said of Cabrera. "He's one of those guys that's really tough to replace. He had a tremendous year for us. That's tough."
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.