Do baseball players need all these days off?

[Paluka]

One thing fantasy has really made me notice is the random days off that so many players seem to take. Guys have great years and making a lot of money just not being in the lineup for 10% of the games. Is this just some old school baseball thing "the guy needed a day off" or is there some reason for this? Today in the Arizona/Philly game I had Burrell/Tracy/Byrnes all sit out and every one of them is young and healthy.