While facing Boston reliever Robbie Ross in the fifth inning, Yanks shortstop Didi Gregorius fouled off an 0-2 pitch that flew into the third-base-side box seats and appeared to strike the fan in the forehead area. Park employees and medical personnel quickly applied first aid to the unidentified woman, who was bleeding.
After a few minutes, the fan was able to stand up and walk away under her own power while keeping an ice compress held against her forehead.
According to television station WCVB, the woman was "alert and conscious" when she was taken to Beth Israel Deaconess Hospital, said Red Sox vice president Charles Steinberg.
After grounding out to the shortstop, Gregorius handed his bat over the Yankees' dugout, and it was passed back to the fans seated with the woman.
"There's nothing I could do about it, so I finished my at-bat, handed them my bat, and obviously they said thank you and everything," Gregorius said. "There's nothing else I can do right there. It's always a little worry."
Red Sox manager John Farrell also expressed his concern for the fan's well-being.
"You see a foul ball go into the seats like that, your thoughts are with her and her family," Farrell said. "The last word I got, she's conscious, she walked off on her power. That's the most recent I've got. Our thoughts are with her for sure -- her and her family."
On June 5, a fan named Tonya Carpenter left the park in serious condition after a shattered bat hit her in nearly the same section of seats. Carpenter spent a week in the hospital while recovering from her injuries.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, follow him on Twitter @IanMBrowne and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.