Much of what was said about Mariano Rivera applies for Derek Jeter. The Yankees won't find someone any better to replace him and they certainly won't find anyone with the playoff experience that Jeter possesses.
Sure, they will have to pay a lot of money for a shortstop who didn't put up huge numbers last year, but there are mitigating circumstances to consider.
Namely, Jeter is the leader of this team, and his captaincy is important to the success of the Yankees.
Also, last year could have been a fluke. I realize he's about to be 37 and a year like this is probably an indication of things to come, but in 2009 he enjoyed an MVP caliber season. I find it hard to believe that it all went this bad, this fast, permanently for Jeter.
Finally, his name and brand are so tied to the Yankees that I don't think he would ever leave. Sure, his agent Casey Close publicly says that he needs to be paid handsomely, but would Jeter really leave?
His popularity is owed directly to the Yankees. If he's playing for the Brewers next year, he will be just another old shortstop. As a Yankee, he can continue to live in the spotlight and produce in October.
A team like the Yankees can get away with Jeter at shortstop even if his 2011 regular season looks like his 2010 regular season, because Jeter is built for October baseball. The Yankees will make the playoffs and they'd have a much better chance of reclaiming the World Series title with Jeter in the lineup.