Maton, who had a 3.84 ERA in 67 games this season, on Tuesday told reporters that he had surgery Monday after suffering a fractured fifth metacarpal in his right pinkie when he punched his locker out of anger last Wednesday.
"It was a short-sighted move and, ultimately, it was selfish," Maton told reporters about the incident after the Astros' regular-season finale. "It's one of those things that I hope doesn't affect our team moving forward."
The 29-year-old Maton gave up two hits, including a single to younger brother Nick Maton, and two runs while recording one out in the eighth inning of Houston's 3-2 win over the Phillies last Wednesday.
Smith, who was acquired from the Braves at the trade deadline, had a 3.27 ERA in 24 appearances for Houston this season.
The rest of Houston's pitching roster is: Game 1 starter Justin Verlander, Valdez, Game 3 starter Lance McCullers Jr., Luis Garcia, Jose Urquidy, Cristian Javier, Ryne Stanek, Ryan Pressly, Bryan Abreu, Rafael Montero and Hector Neris.
Valdez, who won a career-high 17 games this season to rank second in the AL behind Verlander, had 25 straight quality starts from April 25 to Sept. 18 to set the MLB record for most consecutive in a single season. His 31 starts were a career-high and his 2.82 ERA ranks second-lowest of his career and sixth in the AL.
Brown, Hensley, Montero and Neris are making their playoff debuts, as are Houston rookie shortstop Jeremy Pena and utility player Trey Mancini, a six-year veteran acquired this summer after spending his entire career in Baltimore, and infielder Mauricio Dubon.
Houston will carry two catchers, eight infielders and four outfielders in this series.
The Mariners went with the same roster they did for the wild-card series. They will carry 12 pitchers, three catchers, five infielders, four outfielders, and utility players Adam Frazier and Dylan Moore.
Their pitching staff for this series comprises Game 1 starter Logan Gilbert, Castillo, Diego Castillo, Matthew Boyd, Matt Festa, Matt Brash, George Kirby, Andres Munoz, Penn Murfee, Robbie Ray, Paul Sewald and Erik Swanson.
The Mariners have yet to announce a starter for Game 3.
Luis Castillo won Game 1 of Seattle's wild-card series against Toronto. Acquired from the Reds just before the trade deadline, he allowed six hits and struck out five in 7 1/3 shutout innings against the Blue Jays.
Castillo was 8-6 with a 2.99 ERA in 25 starts between the Reds and Mariners this season.
The Associated Press contributed to this report.