I'm sure you didn't miss the Cubs agreeing to a deal with Jon Lester, but just in case -- the two sides have agreed to terms on a six-year, $155 million contract. That's rough news for the Pirates, not even primarily because it makes the Cubs contenders (they probably still aren't, at least not in 2015, although they certainly have enough terrific young hitting talent to prove me wrong if all goes well), but in that the signing should make the Cubs four or five wins better next year. The Cubs play the Pirates 18 times, so the Lester signing effectively subtracts about half a win from whatever the Pirates' projected total will be.
There might be ways for the Pirates' other divisional opponents to compensate for that -- the Reds dealing a couple of starters would help. But Lester joining the division is bad for the Bucs, especially in an offseason in which they mostly seem to be trying to retain the talent they already had (Russell Martin, Francisco Liriano, Edinson Volquez) rather than adding to their talent base.
That's not a criticism -- the Pirates are in this position of trying to maintain rather than upgrading mostly because their previous free agent signees have been so good they're beginning to price themselves out of the Bucs' market. But in the end, this offseason is likely to make the Pirates and Reds worse while the Cubs get much better.