Martinez, after being struck on the left thumb by multiple foul balls off the bat of Giants hitters, left the game in the bottom of the fourth inning. The news didn't get any better after that, as X-rays revealed a fracture of the distal phalanx bone in his left thumb.
The Red Sox have an off-day Monday, at which point Martinez will be examined in Boston by the team's medical staff. At this point, it is not a certainty Martinez will have to go on the disabled list.
"I don't think I have to be on the disabled list," said Martinez after the Red Sox beat the Giants, 5-1. "It's painful, but we'll see how it feels tomorrow. With us having an off-day tomorrow, I'll get it checked out again and we'll see what happens."
The first foul tip that struck Martinez was from Pablo Sandoval in the bottom of the second inning. It caromed off his glove and off his left foot. Martinez, who severely bruised his left big toe a month ago at Tampa Bay, hobbled all the way to the pitcher's mound in agony. But he told manager Terry Francona and athletic trainer Mike Reinold he could stay in the game.
In the bottom of the third inning, Andres Torres of the Giants hit a foul tip that again hit off Martinez's thumb, and that was likely the one that caused the fracture.
Martinez tried to warm up Red Sox lefty Jon Lester in the bottom of the fourth, but his thumb was so swollen that he couldn't properly close his glove. That is when Francona removed Martinez from the game and inserted Jason Varitek.
"There are ways to pad it and things like that," Francona said. "It's not a given he will go on the DL. Now, it's not a given that he's going to be OK, either. We'll get him examined tomorrow and see where we go from there."
Dustin Pedroia, Boston's star second baseman, left Friday night's game when he fractured the navicular bone of his left foot with a foul ball. Clay Buchholz, who leads the Red Sox with 10 wins, had to leave Saturday's game in the top of the second when he hyperextended his left knee running the bases.
"It's unbelievable," said Red Sox slugger David Ortiz. "It's crazy, you know, with all the injuries that have showed up at once. We have to go through that every year but we don't need that right now, you know what I'm saying?"
Martinez, who is known for his high threshold for pain, hopes for a speedy return to the lineup.
"There's nothing that you can do about that," Martinez said. "Everybody knows that you're going to be hurt sometimes. We just need to keep playing hard and keep playing our game, and whatever happens happens."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.