The Messenger - Henry Hack - Bog

Major league baseball superstar Hal Logan is chosen by space aliens to deliver a message to save the human race from extinction... if they heed it.
Hal Logan is a promising high school baseball center fielder nicknamed the "Golden Boy," and he has accepted a sizable bonus to play for the New York Mets after he graduates. Coming home from the last graduation party, the Jeep he was riding with his three athlete friends gets involved in a horrific accident resulting in the deaths of two of them and leaving Hal, and his best friend, Billy Jenkins, with crippling injuries. While surviving the accident, neither Hal nor Billy will ever play sports again.
Five years later, Hal is a college graduate planning to teach high school science, when an alien spacecraft crashes and begins to burn in the yard of his grandparents' mountain home. Hal rescues the pilot who is a teen-aged alien from our galaxy. He is rewarded by being totally cured of the burns suffered in the rescue and of his previous crippling injuries, allowing him to pursue his dream once more.
Fourteen years later, the aliens return and ask the now-famous baseball superstar Hal Logan to deliver a message to the world that will save mankind from its impending destruction from climate change and overpopulation-if they heed it.