The Cleveland Indians had the Cy Young award winner each of the last two seasons:
2007 CC Sabathia
2008 Cliff Lee.
Each was traded during the following season.
What the heck is that?
What a terrible system. The rules have been perverted to such an extent that teams trade their best players during the regular season. Other rules almost compel both players and teams to achieve financial advantage by having long time team favorite players leave and play for an other team. On this the NBA and NFL are no better. However, MLB has by far the worst in season problem. In 1997 Mark McGwire was traded by Oakland to St. Louis; he finished with 58 home runs, the third highest total to that point in MLB history.
Fans buy season tickets and in many cases have the players they want to see most traded before the MLB July 31 trading deadline. Fans should sue. This has been the norm since MLB went to three divisions plus a wild card team, doubling the number of playoff teams.
So far the two New York teams have been exempt but it's only a matter of time before the Yankees and/or Mets trade fan favorites during the season. Then you will hear a lot of complaining. MLB will then need to address this when the biggest market has lame duck teams playing out the final third of the season minus some star players.
MLB should not allow in season trades. Simple and fair.