Washington (AFP) - Jeremy Pena’s solo home run in the 18th inning on Saturday lifted the Houston Astros over Seattle for a Major League Baseball playoff sweep, while Philadelphia ousted defending champion Atlanta.

Pena’s blast after the most scoreless innings in MLB playoff history gave the Astros a 1-0 victory over the Mariners and a 3-0 sweep of their best-of-five American League division series matchup.

Houston reached the best-of-seven AL Championship Series for a sixth consecutive year and will face either the Cleveland Guardians or New York Yankees.

Cleveland rookie Oscar Gonzalez hit a two-out, two-strike single with the bases loaded in the ninth inning to drive in two deciding runs in a dramatic 6-5 victory over the visiting Yankees.

“I just wanted to put the ball in play. Thank God I got the results,” the Dominican said through a translator. “Then I was just waiting for the guys to score and celebrate.”

The Guardians swiped a 2-1 series lead with the chance to advance by winning at home on Sunday.

In the National League, Philadelphia defeated Atlanta 8-3 to win their series in four games.

J.T. Realmuto hit an inside-the-park home run while Brandon Marsh smacked a three-run homer and Bryce Harper added a solo homer for the Phillies.

Philadelphia advanced to an NL finals showdown against either the Los Angeles Dodgers or San Diego Padres to decide a World Series berth.

“What an opportunity,” Harper said.

“You’ve got to beat the champs to be the champs. I get chills, man. We’ve got two more. We’ve got (to win) eight more games.”

The Phillies reached the playoffs for the first time since 2011 and made the NL final for the first time since 2010. They last reached the World Series in 2009 and last won the crown in 2008.

The Braves failed in their bid to become the first MLB repeat champion since the New York Yankees from 1998-2000.

The Dodgers, who won an MLB-best 111 games this season, faced elimination in a later game at San Diego.

At Seattle, relief pitchers were masterful for hours in the first MLB playoff game to go scoreless into the 16th inning. The total of 42 strikeouts in the contest also was an MLB playoff record.

The Astros stranded 13 base runners and the Mariners left 10 on base through 17 scoreless innings.

In the 18th, Pena blasted a 3-ball, 2-strike fastball pitch off Seattle reliever Penn Murfee over the centerfield wall for the only run of the contest.

At Cleveland, the Guardians took a 2-0 lead on a run-scoring single by Josh Naylor in the first and another by Steven Kwan in the second.

Aaron Judge and Oswaldo Cabrera each blasted two-run homers to put New York ahead 4-2. Will Brennan answered with a run-scoring single in the sixth but Harrison Bader’s solo homer in the seventh made it 5-3 Yankees.

Cleveland answered in the ninth on consecutive singles by Myles Straw, Kwan, Amed Rosario and Jose Ramirez to pull the hosts within 5-4 and load the bases, setting the stage for Gonzalez’s heroics.

- Inside-the-park mark -

At Philadelphia, Realmuto became the first catcher to hit an MLB playoff inside-the-park homer and only the 18th player in all to manage the feat. It was the first such homer in the playoffs since 2017.

Marsh gave the Phillies the lead by hitting a three-run homer in the second inning off Braves pitcher Charlie Morton, making his first playoff start since suffering a broken right leg last October.

Morton, who left the game after a batted ball struck his right elbow in the second inning, was replaced by Collin McHugh, who surrendered Realmuto’s inside-the-park homer in the third.

The ball went over Atlanta’s Michael Harris and bounced off the centerfield wall, rolling away from Harris.

By the time he retrieved the ball and threw it to the infield, Realmuto was racing home in a 15.4-second circuit of the bases to give Philadelphia a 4-1 lead. The Braves never got nearer than two runs again.