As Roger Clemens reached the end of his career, he returned to the Astros (and later the Yankees) later in the season to contribute to the team in a full-time role for about 2/3 of the season. Similarly, Pedro Martinez did the same thing for a couple months with the Philadelphia Phillies.
Was it injury that made these players opt to do this? No, it was opportunity and teams willing to work with their needs. Clemens wanted to spend more time with family. Pedro wanted to contribute.
With past experience and precedent as a guide, I think we will see Andy Pettitte return to baseball mid-season. He retired to spend more time with family, but he still had some life left in baseball. The Yankees have a need with injuries and reliability issues, and there could be an appropriate match for both the Yankees and Pettitte to come to an agreement for a June or July return.
In business, many companies will overlook someone because they are only available part of the year, part-time, or for a limited role. Baseball’s situations above remind us that if there is a need and a talent to meet that need, reasonable accommodations can be made to enable both parties to benefit.