The accident occurred Tuesday as Valentine was reading a message from second baseman Dustin Pedroia, The New York Times reported.
The manager was riding on a rain-slicked path in the Central Park Reservoir before the start of Tuesday night's game against the Yankees. Pedroia had sent him a text saying he would play in the game that night despite a broken left ring finger.
Engrossed in the message, Valentine did not see the umbrellas of two French tourists ahead of him. When he finally saw them, he swerved to avoid them, skidded on the wet pavement, lost his balance and ended up somersaulting with his bike down the side of a hill.
Valentine was wearing a helmet and sustained injuries to his knees and hips.
Showing up at the game with bandages on his legs, the manager said if Pedroia "can play with that, I can certainly manage with this."