Secondary thoughts re: Hamels. I think there's a very good chance they pick up his 2019 option. Given Texas is eating $9 mil of the remaining $14 mil($8 this year plus $6 mil buyout next), that effectively means you're paying him $5 mil the rest of 2018 and if you choose to pick up that option next year he costs you $14 mil. Chatwood is making $12.5 mil. So, as prices go if he's decent the rest of the way that's not a bad price to pay.
However, if we also assume your 1-3 is Darvish, Lester, and Hendricks with Hamels returning then you suddenly have a **** ton of pitchers. I mean you're talking about Q, Monty, Chatwood, Smyly and probably Alzolay all in the mix for one rotation slot. Given there's only 3-4 interesting FA pitchers(gio gonzo, kershaw, Corbin and Keuchel), that could lead to some interesting possibilities trade wise. I doubt they have a way to use those 5 pieces to turn into another TOR pitcher. but you might be able to move say Monty for a back end top 100 guy and something else and then replace his role with Smyly. Then you could have Q and Chatwood battle it out for the #5 slot with Smyly as a swing arm as needed and Alzolay continuing to develop in AAA. You might even go more aggressive than that. If you really like Alzolay you could consider moving Monty and Q and have Alzolay, Chatwood and Smyly battle it out for the #5. I think a team like SD who's got a great farm system but could use some players ready today offers an interesting team to potentially deal with.
Just an interesting thought I had when considering Hamels' potential impact.