Media Translation Service provided free of charge here at YB.com:

When a member of the media says:

"The Yankees could have a serious clubhouse problem on their hands with a potentially dissatisfied Gary Sheffield...."

The media member is really saying:

"The Yankees' procurement of Abreu without sacrificing top prospects was a huge win for New York. I can't find a downside to this deal. Furthermore, it's really scary for the rest of baseball that Brian Cashman is a highly competent GM who is clearly now in full control of the vast resources at the Yankees' disposal. Therefore, I'm fabricating something about the mood of a player who is a) given to public statements and b) will likely not take another at-bat this season."