The answer to the question posed in the headline is: “Nothing.”
Well, that’s not entirely true. Perhaps I should have said, “Probably nothing.”
The Cubs went into this offseason needing two starting pitchers, with the departure of Jake Arrieta and John Lackey via free agency. One thing the signing of Tyler Chatwood does likely mean is that we’ve seen the last of Jake in a Cubs uniform. That was something that was pretty obvious to me when the season ended, though I know some held out some hope for Jake’s return. But with Chatwood taking up $13 million worth of the Cubs’ payroll for 2018, it seems management has made the statement that they’re moving on without Jake. (Lackey was unlikely to return in any case and certainly won’t now.)
But the Cubs are still looking for one more starting pitcher. They’re still in the Shohei Ohtani sweepstakes, until they’re told they’re not, and have been linked to former Rays starter Alex Cobb.
I don’t think the signing of Chatwood means anything toward the Cubs’ interest in those two pitchers. They can still be interested in both.
However, what it does likely mean is that both won’t be Cubs unless the Cubs plan on going with some sort of six-man rotation. That’s certainly not impossible, especially if the Cubs do win the Ohtani sweepstakes. Ohtani has been accustomed to a six-man rotation in Japan and perhaps the Cubs could come up with a six-man plan. Such a plan would also give good rest to the other starters; you saw how worn down everyone seemed at the end of 2017.
The way it appears to me is this, and certainly I could be wrong: The Cubs are waiting for Ohtani to make his decision. If he chooses the Cubs, they might decide to be out on Cobb, saving that money for someone else (Wade Davis, perhaps?). They’d still have Mike Montgomery available to slot in as a starter at times to make a modified six-man rotation.
If the Cubs lose out on Ohtani, at that point I’d expect them to go all-out to sign Cobb.
So the answer isn’t really “nothing.” The Cubs do have some choices to make, and those choices might have to be made fairly soon.
At least we now know the Cubs have four rotation starters lined up for 2018. Here’s some video of Chatwood striking out some Texas Rangers in 2016.