Is Jon Lester's decision down to Red Sox and Cubs (and the Mystery Team)?

Jon Lester's free agency saga is expected to come to a close before the week is done, and might be down to just the Cubs and Red Sox, according to Sean McAdam:

As the bidding currently stands, the Chicago Cubs are said to have the biggest offer on the table ($138 million over six years), just ahead of the Red Sox proposal of six years and $130 million.

The nature of the Giants' offer for Lester is unknown

While the Giants can't be dismissed -- they've won three World Series in the last five years and offer a pitching-friendly ballpark -- many in the industry view Lester's choice coming down to the Cubs and Red Sox.

If, indeed, this is how things stand, then the decision for Lester seems to be straightforward: go to the National League and get slightly more money in the process, or return to the team he rose through the ranks and spent the first nine years of his career with on a slight home-team discount.

That's a fairly big "if", though. For one thing, we actually haven't heard of the $130 million offer McAdams cites. We have heard that the Red Sox are willing to go to six years, and we have heard that they'll be going to "at least" $130 million, but it's not quite the hard-and-fast final offer it's made out to be here. The same can likely be said about the Cubs' bid.

The other question mark is whether or not McAdam's sources are factoring in the Mystery Team that Peter Gammons mentioned recently. Gammons' speculation comes from a small group of general managers, and if they're simply reading the signs and inferring the existence of this team rather than speaking from any personal knowledge, then it seems unlikely McAdams' sources have made that leap. On the other hand, if there really is another club in the race, then it's entirely possible that they're just dismissing that club--possibly a sign that they're in it just to drive up the price.

Or Gammons' guys could just be completely off-target and it really might just be Cubs vs. Red Sox. Except that even McAdams, free from any "Mystery Team" discussion, can't help but bring it back to the Yankees:

Looming over the talks is the specter of the New York Yankees, who have a history of swooping in at the 11th hour to land big-name free agents. The Yankees have a thin rotation that include three established starters -- Ivan Nova, CC Sabathia and Masahiro Tanaka -- all returning from injuries.

Moreover, the Yankees traditionally feature a high-end lefty stater as part of their staff, and if the Yankees are concerned with forfeiting a draft pick next June, Lester comes without any compensation since he was traded in the final year of his existing deal.

It's downright scary how close that is to the description of a Mystery Team--the type that could snap Lester away from both the Cubs and Red Sox with a truly ridiculous offer. And one that would really hurt at the end of the day.

At the very least, though, we shouldn't have to worry much longer. Either Jon Lester will be a member of the Red Sox by the end of the week, or the Sox will be moving onto Plan B, and hoping they didn't just lose an ace to their greatest rivals.