On the year, his first with the Cubs, Chatwood now has a 4.98 ERA over 94.0 innings and 19 starts.
He was 5-2 with a 2.45 ERA in 18 games this year at Class A South Bend and Class A Myrtle Beach. He is now at the team's High A team in Myrtle Beach.
The deal is pending physicals for all players involved.More news: Celebrities dazzle at Akash-Shloka's engagement party
Earlier in the day, the Cubs tried to make a play for starter J.A. Happ but the Yankees won out for the veteran starter.
"To be able to change kind of the mindset, now to go on a first-place team, there's something inside of you that sparks when you get in those situations", Hamels said at the Rangers ballpark after the trade was announced.More news: 'What do we got to pay?' Inside the Trump-Cohen tape
Hamels also has to be more reliable than Yu Darvish, who's slowly rebooting his rehab process and looking more like a September call-up than a pitcher the Cubs are actually counting on this year.
Lacy, 23, was the Cubs' 11th round pick in the 2017 draft. A four-time All-Star, Hamels is 152-111 with a 3.43 ERA in his 13th season in the league.
In his last home start for Texas before the deadline, Hamels allowed seven runs on Monday night against Oakland. The Cubs emptied their once rich farm system on the way to three straight NLCS appearances and a historic championship in 2016, hurting their chances of making a major trade this year. He was 1-1 with a 4.08 ERA in eight appearances with the Cubs and pitched a scoreless ninth in Thursday's 7-6 comeback win over the Diamondbacks.More news: Facebook reports slower-than-expected 2Q revenue growth
"It's always that chase for that World Series, you start realize how hard it is to achieve", Hamels said.