Mr. Wellington by David Rabe, illustrated by Robert Andrew Parker

From chapters.ca:
Young Jonathan finds a small, frightened squirrel on the road and brings it home tucked inside his sneaker. But the squirrel, named Mr. Wellington, is weak and listless, and fearful of the unfamiliar surroundings. Told from alternating perspectives - Jonathan's and Mr. Wellington's - this beautifully written story, enhanced with pen- and- ink wash illustrations, has all the markings of an enduring classic animal tale.