Not too surprising, players are some of the biggest memorabilia collectors.
Willis and Miguel Cabrera often are sought out to sign and exchange jerseys. Willis has amassed upward of 40 from his peers.
The protocol varies. Willis and Cabrera are among the players who purchase their own jerseys in bulk at about $100 apiece to give them away when asked. What most guys do is buy the jersey they want on their own. Before a game, one of the clubhouse attendants will run it over and get it signed.
Players generally bring enough bats on the road where they can spare one or two. Jerseys are another matter.
Since the clubs never provide the jerseys it is up to players to buy them in order to get them signed. Some are collectors while others auction them off to benefit their favorite charities. But for whatever the reason, baseball players are some of the biggest fans of baseball players.