HOUSTON -- There were moments early in the American League Championship Series when it felt like the Houston Astros were one play away from stumbling into a serious hole against the New York Yankees. But the final moment belonged to Jose Altuve, and the Astros are AL champions.

Altuve blasted a two-run, walk-off homer with two outs in the bottom of the ninth off Yankees closer Aroldis Chapman, igniting a raucous crowd and sending Houston to the World Series for the third time in franchise history and second time in three years. The Astros won 6-4, clinching the pennant in six games.

Altuve said the homer was probably his best career moment to date, but he still wouldn't take credit for the win.

"I have to say No. 1 because we're going to the World Series," Altuve said. "But we're not going to the World Series because of me. We're going to the World Series because of everybody inside of the clubhouse."

It was not easy.

With the Astros two outs from the flag, Yankees second baseman DJ LeMahieu battled closer Roberto Osuna for 10 pitches before finally lofting a high-arching fly ball that just cleared the right-field fence. It was a two-run shot, and it knotted the score at four. As it turned out, LeMahieu was only setting the table for Altuve's heroics.

The game marked the first time in postseason history that a team hit a game-tying or go-ahead home run in the top of an inning, then allowed a game-ending homer in the bottom of the same inning. It made for a whirl of emotions, but when you've got Altuve on your side, managing those emotions is a bit easier.

"I was sitting on the stairs and I looked at [Michael Brantley] after the 2-0 pitch and said 'Jose is gonna win it for us,'" Astros outfielder Josh Reddick said. "He's the glue to this team. He holds us all together and gets us going."

The clincher fueled a sellout crowd at Minute Main Park under the roof on an autumn night in Texas. The pregame whistles and train toots and towel waves had barely subsided when, after a snappy 1-2-3 first inning for Houston opener Brad Peacock, Yuli Gurriel lined a three-run homer into the Crawford Boxes in left field.

The quick start left the Yankees scrambling to catch up all night in what turned out to be a futile effort to save their campaign. Finally, LeMahieu's great at-bat brought New York even -- at least for a few minutes.

For Altuve, the storybook finish provides another shining bullet point on a career résumé that already seems stacked enough to eventually land him in the Hall of Fame. If it takes one Hall of Famer to know another one, count Astros great Craig Biggio as a believer.

"The greatest thing about Jose is Jose," Biggio said amid the celebration on the field after the game. "He's just a great human being. He gets in the heat of the moment and rises to the occasion. He's an incredible player."

The Astros capped their third straight 100-win season with another AL title, and in doing so, they ensured that the Yankees go without a pennant in the 2010s -- their first decade without a league title since before they acquired Babe Ruth in 1920.

Instead, it's Houston that might someday be remembered as the team of the decade that's coming to a close.

For that to happen, Houston needs to take one more step, and the Astros are well aware that they have unfinished business.

"We're not done yet," Astros general manager Jeff Luhnow said. "This series could have gone either way. The last series could have gone either way. We knew we had built a team to win, now we get a chance to prove it."

Houston defeated the Yankees in the ALCS for the second time in three seasons. In doing so, the Astros knocked New York out of the postseason for the third time in five years -- something no other team has done to the Bronx Bombers.

As for those moments of vulnerability: Initially in the series, the Yankees seemed poised to knock off the top-seeded Astros. They routed Houston 7-0 in Game 1. In Game 2, the teams battled in a grueling 4-hour, 49-minute affair that finally ended when Carlos Correa homered on the first pitch of the 11th inning. The Astros never trailed in the series again. The Yankees missed their opportunity, which may have been the theme of the series for them.

"It's the biggest thing I look back on is that we left eight or nine in this game on base," Yankees slugger Aaron Judge said after his team was eliminated. "Even throughout the whole series, we left a lot of guys on base and had a lot of missed opportunities."

After 107 regular-season wins, the Astros ended up where the consensus figured them to be -- at least, the consensus of baseball pundits and the betting markets. Their path was rocky at times -- the five-game AL Division Series against Tampa Bay, the early struggles against New York -- but that's how October baseball goes. Now Houston is positioned to stake claim to the dynastic throne the Yankees have occupied so often in baseball's history.

"We said all along our goal was to win multiple championships," Luhnow said. "We're not there yet. We've won one. We're going back to another. Hopefully, we'll get that done."

With the pennant secured, the Astros will open the World Series at home on Tuesday against the well-rested Washington Nationals. Washington completed its four-game sweep of St. Louis on Oct. 15 -- the night Houston and New York played Game 3 of their six-game tussle. The Nationals are making their World Series debut.

Game 1 of the Fall Classic should be a premium pitching matchup: Houston figures to send Gerrit Cole to the mound, now that he won't have to start Game 7 against the Yankees on Sunday.

Of course he was happy about it. When asked if this was the happiest he'd ever been to not get to make a start, Cole leaned back and issued an emphatic, "Yes!"

The Nationals will likely counter with Max Scherzer, making the Series opener the first of a series of high-profile pitching confrontations.

"It's incredible," Astros starter Justin Verlander said. He's lined up to start Game 2, likely against Washington's Stephen Strasburg. "I keep saying incredible, but it really is. The Nationals have a great rotation, have a great four starters. I like our rotation as well. It should be a great series."

The starting pitching will be the initial dominant storyline of the World Series, but ironically, the Astros clinched the pennant on a night when both managers went to a bullpen day in lieu of a traditional starter. Peacock opened for Houston, giving up one run in 1⅔ innings. Meanwhile, Chad Green threw the first inning for New York and gave up Gurriel's home run. The Yankees fell to 12-6 in opener games, including the postseason, and Houston won one for the first time in three tries.

The strategy smacked of 2019 baseball: According to Elias, the most recent postseason game in which neither starting pitcher threw at least two innings was Game 4 of a 1999 ALDS between the Red Sox and Indians.

That the Astros won a bullpen game against a Yankees team with one of the most feared relief staffs in baseball is hardly a surprise. That's the Astros: They win in ways old and new and in ways big and small.

"It was fun," Luhnow said. "It was a fun baseball game for a lot of reasons. I don't know how many pitchers we used in total, but it meant that the managers had to be really wise about when to take their pitchers out. This game could have gone either way, but we had Altuve and they didn't. That ended up being the difference."

Now, things are about to get as big as they get in baseball: the World Series. This time, it's between a team trying to secure its place atop the mountain and another trying to ascend to that peak for the first time. The bad news for the Nationals is that the moments of vulnerability for the Astros might have already passed.