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The Houston Astros and Seattle Mariners might be AL West rivals, but they hooked up for a four-player trade Tuesday. The Astros sent infielder Abraham Toro and right-handed reliever Joe Smith to the Mariners for righty relievers Kendall Graveman and Rafael Montero, the teams have announced.

"Adding a young Major Leaguer like Abraham, as well as the veteran presence and experience of Joe Smith is a move we feel makes us a deeper team today, as well as moving forward," Mariners GM Jerry Dipoto said in a statement. "We are certain to be very active in the hours and days ahead as we remain committed to making moves that will enhance our chances over the season's final 60 games and hopefully beyond."

Coincidentally enough, the Astros and Mariners are playing the middle game of a three-game series at T-Mobile Park on Tuesday night, so the players only need to change clubhouses to join their new team.

Houston addresses its season-long need for bullpen help with Graveman, who has been among the game's best relievers this year. The 30-year-old free-agent-to-be has allowed three earned runs in 33 innings this season while striking out 34 and walking eight. He figures to immediately step in as closer Ryan Pressly's setup man.

Not surprisingly, the decision to trade Graveman to a division rival is reportedly not going over well inside Seattle's clubhouse.

Montero, 30, was designated for assignment over the weekend after allowing 39 runs in 43 1/3 innings with Seattle. He was effective with the Rangers, another AL West team, the last two years, however, pitching to a 3.09 ERA in 46 2/3 innings. The Astros can retain Montero as an arbitration-eligible player in 2022 should he get back on track.

"It's a move that we feel improves our roster, but we are going to continue to spend the next three days hopefully finding additional moves to improve the roster," Astros GM James Click told reporters, including Chandler Rome of the Houston Chronicle.  

For the Mariners, they get a veteran reliever in Smith to help replace Graveman. The 37-year-old has struggled this season, allowing 18 runs in 21 2/3 innings. His track record suggests he's much better than that. Smith will become a free agent this winter and has been death on righties throughout his career.

Toro, 24, has struggled in parts of three MLB seasons, hitting .193/.276/.350 with 11 home runs in 308 plate appearances. He's a first and third baseman and figures to see more playing time at the former. Kyle Seager is entrenched at third base and first has been a revolving door most of the year.

Seattle's bullpen has been among its greatest strengths this season, with Graveman joining Paul Sewald and Drew Steckenrider to form a dominant end-game trio. The bullpen is a little weaker now without Graveman, so the Mariners are betting on Smith and others to pick up the slack.

The Astros come into Tuesday with an AL West leading 61-40 record. The Mariners are six games back at 55-64, though they're only one game behind the Athletics for the second wild card spot.