Francisco Alvarez's solo home run in the bottom of the ninth inning lifted the New York Mets to a dramatic 4-3 win over the Baltimore Orioles in Monday's opener of an important three-game series for both teams.

With one out and the game tied at 3-3, Alvarez crushed a 3-0 fastball from Seranthony Dominguez well clear of the wall in left center field to allow the Mets to close the gap in the National League wild card race and knock the Orioles out of first place in the American League East.

J.D. Martinez had a two-run homer in the first inning for New York, which moved within 1 1/2 games of the Atlanta Braves for the NL's final wild card spot with its third win in four games.

The Orioles have now lost three of four and dropped a half-game back of the idle New York Yankees for the AL's top spot.

Baltimore made it interesting, however, by scoring twice in the seventh inning to erase a 3-1 deficit.

Ryan Mountcastle began the rally with a lead-off double and took third on a groundout before being forced home when Mets starter David Peterson was called for a balk. Ramon Urias then followed with a solo home run to knot the score at 3-3.

Peterson had been cruising up until that point and departed after allowing three runs - two earned - while striking out eight through seven innings.

Martinez followed a first-inning single by Mark Vientos with his 13th homer of the season to give the Mets an early advantage. They increased the margin to 3-0 in the fourth when Pete Alonso doubled and later crossed the plate on Tyrone Taylor's two-out single.

The Orioles answered in the fifth with the help of an error by Peterson, who threw errantly on a pickoff attempt to send Urias to third after the infielder reached on a double. Urias would then score on a groundout by Jackson Holliday.

Urias and Mountcastle each finished with two hits for the Orioles, while Baltimore starter Trevor Rogers struck out five while permitting three runs in 4 2/3 innings.

Diaz's homer in ninth caps rally, keeps Astros hot

The Houston Astros also earned a key win via a walk-off home run, as Yainer Diaz's ninth-inning blast gave the AL West leaders a 5-4 comeback victory over the Boston Red Sox.

Houston scored once in each of the final two innings to rally for its 11th win in 12 games, with Diaz delivering the final blow by launching Kenley Jansen's pitch well over the left field wall with one out in the bottom of the ninth.

The Astros tied the game at 4-4 with a two-out rally an inning earlier, as Chas McCormick singled off reliever Lucas Sims and stole second before racing home on Mauricio Dubon's clutch single.

Yordan Alvarez and Victor Caratini each collected three hits to help Houston increase its lead over the second-place Seattle Mariners to five games in the division.

The slumping Red Sox lost for the eighth time in 12 games despite taking a 4-2 lead on Masataka Yoshida's pinch-hit two-run homer off reliever Tayler Scott in the top of the sixth inning. Romy Gonzalez was aboard for the blast after reaching on an error by Houston second baseman Jose Altuve, one of a season-high four miscues for the Astros.

Houston got closer in its half of the sixth, however. Back-to-back singles by Jeremy Pena and Caratini put runners on first and third for Jon Singleton, who drove in Pena with a sacrifice fly to trim the lead to 4-3. 

Astros starter Yusei Kikuchi struck out seven over 5 2/3 innings while allowing three runs, one earned, though his night began ominously when Boston's Jarren Duran connected on his 16th homer of the season on the game's first pitch.

Rob Refsnyder and Rafael Devers each singled later in the first inning before another Houston error - a misplay by rookie third baseman Shay Whitcomb - enabled another run to score.

The Astros were held scoreless by Tanner Houck through the first three innings before breaking through in the bottom of the fourth, which Alvarez began with a double and Diaz followed with a single. Alvarez was later thrown out at home on a fielder's choice grounder, but Caratini singled in Diaz and Pena also scored on the play on an errant throw by Boston catcher Danny Jansen.

Houck worked six innings and struck out eight while surrendering three runs - two earned.

Stone, Muncy propel Dodgers over Mariners in Turner's Los Angeles return

Gavin Stone racked up a career-high 10 strikeouts in seven innings, Max Muncy homered in his first game back from the injured list, and the Los Angeles Dodgers spoiled Justin Tuner's return to Dodger Stadium with a 3-0 win over the Seattle Mariners.

Muncy, sidelined since May 16 by a right oblique strain, came through with a two-run homer in the seventh inning to back Stone's superb start and help the Dodgers win the opener of this three-game series between playoff hopefuls.

Gavin Lux homered earlier in the seventh to break a scoreless deadlock and a terrific pitching duel between Stone and Bryan Woo, who had allowed just one hit until Lux drove a pitch over the wall in center field.

Woo (5-2) then hit Will Smith with a pitch and was removed in favour of Yimi Garcia, who was greeted by Muncy's towering drive to right that quickly made the lead 3-0.

Stone (11-5) yielded just two hits and two walks before departing, with Joe Kelly pitching a scoreless eighth before Evan Phillips retired the side in order in the ninth to notch his 16th save.

Woo was charged with two runs in 6 1/3 innings in slumping Seattle's sixth loss in seven games. The defeat dropped the Mariners five games back of first-place Houston in the AL West.

Turner went 1 for 3 in his first appearance at Dodger Stadium in nearly two years. The 39-year-old infielder made two NL All-Star teams during a successful nine-year tenure with the Dodgers from 2014-22.