For the second time in three seasons, the Astros and Yankees will square off for the American League pennant.

While the winning culture has remained the same -- these two teams have won more games than any other in the American League over the past three seasons -- plenty has changed since Houston eliminated the Yanks in a memorable 2017 ALCS that went a full seven games.

The Astros' offensive core remains intact, though it now has some additional help, and Alex Bregman has elevated his game to another level. Not to mention Houston's pitching staff has since added Gerrit Cole and Zack Greinke.

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As for the Yankees, their lineup will have a very different look than it had two years ago, when Gleyber Torres was still in the Minors and DJ LeMahieu was in the midst of an All-Star season with the Rockies.

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Here's a position-by-position look at how each team stacks up compared to the 2017 versions:

CATCHER

Astros
Then: Brian McCann
Now: Robinson Chirinos/Martín Maldonado

Chirinos has proven to be a solid addition, putting up nearly identical numbers to McCann's offensive production in 2017. McCann hit .241/.323/.436 with 18 homers in 2017, while Chirinos hit .238/.347/.443 with 17 homers this year.

As for Maldonado, he's helped Cole reach another level since joining the club at this year's Trade Deadline. Including Cole's stellar outing in Game 2 of the ALDS, the Cy Young Award candidate has a 1.41 ERA with 129 strikeouts in 76 1/3 innings when pitching to Maldonado this season. That equates to a staggering 15.2 strikeouts per nine innings.

Yankees
Then and now: Gary Sánchez

No change here, though the Yankees are hoping to see a different version of Sánchez this time around. Though he had a stellar 2017 in which he hit .278 with an .876 OPS and 33 homers, Sánchez went just 5-for-26 (.192) with one home run and nine strikeouts in the '17 ALCS. His OPS dipped to .841 this season, but the backstop clubbed a career-high 34 homers in 106 games.

FIRST BASE

Astros
Then: Yuli Gurriel
Now: Gurriel

Gurriel had an impressive rookie season in 2017, but he's had a far-more-impressive breakout campaign this year. He hit .299 with 18 homers, 75 RBIs and an .817 OPS en route to finishing fourth in AL Rookie of the Year Award voting two years ago, but took his game to another level this year, putting up career highs in home runs (31), RBIs (104), on-base percentage (.343) and slugging percentage (.541).

Yankees
Then: Greg Bird
Now: DJ LeMahieu/Luke Voit

Bird had a respectable performance in the 2017 ALCS, going 5-for-20 (.250) with a home run and eight walks, good for a .464 on-base percentage and .964 OPS. That said, LeMahieu is in the midst of an MVP-caliber campaign after hitting .327 with 26 homers and 102 RBIs in his debut season with the Yankees. The utility infielder settled in at first base in New York's ALDS victory over the Twins, allowing Edwin Encarnación to serve as the club's designated hitter, while Gleyber Torres started at second base and Gio Urshela manned the hot corner.

SECOND BASE

Astros
Then and now: José Altuve

Altuve didn't quite match the numbers from his 2017 MVP season this year, though he did hit a career-high 31 homers. Still, the superstar second baseman is just as dangerous hitting out of the two-spot in Houston's potent lineup. Altuve will be looking to duplicate his success from the '17 ALCS in which he hit .320 (8-for-25) with a pair of homers.

Yankees
Then: Starlin Castro
Now: Gleyber Torres

Castro had an All-Star season in 2017, hitting .300 with 16 homers and 63 RBIs in 112 games, but that production pales in comparison to what the Yankees have gotten from Torres. The 22-year-old phenom crushed 38 homers this season, joining Joe DiMaggio as the only players in franchise history to top the 30-homer mark at age 22 or younger.

The Yankees' revamped infield is a significant upgrade from the 2017 unit, with Torres and LeMahieu leading the charge.

SHORTSTOP

Astros
Then and now: Carlos Correa

Yankees
Then and now: Didi Gregorius

Both teams remain the same at shortstop, where Correa and Gregorius both possess the ability to alter a game -- or an entire series -- if they settle into a groove. Correa and Gregorius both missed significant time due to injuries this season, but both are healthy and ready to contribute.

Correa hit 21 homers this season, despite playing only 75 games, and finished with a .926 OPS during the regular season. As for Gregorius, he took a step back this season after earning a share of MVP votes each of the last two years. Still, he proved he can be a pivotal piece of New York's postseason run with his massive grand slam in Game 2 of the ALDS.

THIRD BASE

Astros
Then and now: Alex Bregman

Bregman put up a respectable .827 OPS with 19 homers and 17 stolen bases in 2017, his first full year in the big leagues. However, the blossoming superstar went 4-for-24 (.167) with one extra-base hit (a double) in the '17 ALCS.

Bregman broke out in 2018 (31 homers, 103 RBIs, 51 doubles and a .926 OPS) before taking his game to another level this year. The AL MVP candidate finished with a 1.015 OPS to go along with 41 homers, 112 RBIs and a Major League-leading 119 walks. Houston may be starting the same player at third base, but the production could be very different this time around.

Yankees
Then: Todd Frazier
Now: Gio Urshela

The Yankees acquired Frazier ahead of the 2017 Trade Deadline in an attempt to bolster their production at third base, where Chase Headley had been the everyday starter since being acquired from the Padres at the 2014 Trade Deadline. Frazier hit .222 with 11 homers over 66 games down the stretch, then went 4-for-22 (.182) with a home run in the ALCS. Urshela seemingly came out of nowhere to hit .314 with 21 homers and 74 RBIs in 132 games this season.

OUTFIELD

Astros
Then: Marwin González, George Springer, Josh Reddick
Now: Michael Brantley, Springer, Reddick

Though González put up MVP-caliber numbers in 2017, hitting .303 with 23 homers, 90 RBIs and a .907 OPS, he hit just .180 in the '17 postseason and went 3-for-22 (.136) with no home runs or RBIs in the ALCS. While González's versatility certainly provided a significant boost during his time with the Astros, Brantley hasn't been too shabby in left field this year. The veteran outfielder earned his third consecutive All-Star nod (and fourth overall) en route to hitting .311 with a career-high 22 homers and 90 RBIs

Yankees
Then: Brett Gardner, Aaron Hicks, Aaron Judge
Now: Giancarlo Stanton, Gardner, Judge

Hicks was phenomenal in the 2017 ALDS against the Indians, but disappeared offensively in the ALCS, going just 2-for-24 (.083) with eight strikeouts. With the 30-year-old outfielder sidelined by a right flexor strain this time around, the Yankees will deploy Gardner in center field between Stanton and Judge at the corners.

Injuries limited Stanton to just 18 games during the regular season -- only 13 of which did both he and Judge participate. With the powerful duo seemingly healthy, it could take an already dangerous lineup to new heights.

DESIGNATED HITTER

Astros
Then: Evan Gattis/Carlos Beltrán
Now: Yordan Álvarez

Houston's DHs went a combined 2-for-23 (.087) in the 2017 ALCS, but the spot certainly does not project to be a weakness this time around. Álvarez burst onto the scene in mid-June, going 8-for-17 (.471) with four homers in his first five career games. He's yet to really slow down, as the 22-year-old slugger finished the regular season hitting .313 with a 1.067 OPS and 27 home runs in 87 games.

Yankees
Then: Chase Headley/Matt Holliday
Now: Edwin Encarnación

Encarnación figures to be designated primarily, if not exclusively, to DH duties for the ALCS after missing the final three weeks of the season due to a strained left oblique. He returned for the ALDS and made an immediate impact with his bat, providing the Yankees with yet another weapon in their potent lineup.

STARTING PITCHERS

Astros
Then: Dallas Keuchel, Charlie Morton, Justin Verlander, Lance McCullers Jr.
Now: Verlander, Gerrit Cole, Zack Greinke

This is by far the biggest difference between the 2017 and 2019 Astros. While Keuchel and Morton were certainly formidable starters behind Verlander, who Houston acquired moments before the '17 Trade Deadline, neither was as dominant as Cole. Along with being among the AL's leading Cy Young Award candidates, Verlander and Cole have combined to produce the league's most dominant starting pitching duo since Arizona's Randy Johnson and Curt Schilling almost 20 years ago.

Greinke may have had a few hiccups since joining the Astros at this year's Deadline -- including in Game 3 of the ALDS -- but the former Cy Young winner and six-time All-Star is still a pretty decent option for a No. 3 starter.

Yankees
Then: CC Sabathia, Luis Severino, Masahiro Tanaka, Sonny Gray
Now: James Paxton, Tanaka, Severino

Sticking with the trend in the Bronx this season, Severino was sidelined for the majority of the regular season due to right rotator cuff inflamation. The preseason Cy Young Award hopeful made his 2019 debut on Sept. 17, and he looked much like the Yankees' ace of the past couple seasons in his limited action down the stretch. Severino's health should certainly provide a boost to the Yankees' pitching staff, as would Tanaka continuing his postseason success (1.54 ERA in six career playoff starts).

BULLPEN

Astros
Then: Chris Devenski, Luke Gregerson, Will Harris, Francisco Liriano, McHugh, Brad Peacock, Joe Musgrove
Now: Harris, Ryan Pressly, Josh James, Héctor Rondon, Joe Smith, Jose Urquidy, Wade Miley

To see the difference in Houston's bullpen from two years ago, look no further than Harris. The veteran right-hander was solid in 2017, posting a 2.98 ERA, but he turned into one of the most dominant relievers in the Majors in '19. Harris finished with a 1.50 ERA over 68 appearances, the second-lowest mark in the Majors among any pitcher with at least 40 innings.

Harris was a big reason why the Astros 'pen finished the regular season with a 3.75 ERA, third best in MLB behind only the Rays (3.66) and Indians (3.67). That's a much different result than in 2017, when Houston's relief corps recorded a 4.27 ERA, ranking 17th in the Majors and 10th in the AL.

Yankees
Then: David Robertson, Dellin Betances, Chad Green, Tommy Kahnle, Adam Warren, Jaime Garcia, Jordan Montgomery
Now: Green, Kahnle, Zack Britton, Adam Ottavino, J.A. Happ, Luis Cessa, Jonathan Loaisiga, Tyler Lyons

Britton and Ottavino have given the Yankees everything they could have hoped for and more. Britton posted a 1.91 ERA over 61 1/3 innings, his best season since his remarkable 2016 with the Orioles in which finished fourth in AL Cy Young Award voting. Ottavino, meanwhile, was brilliant in his debut season in the Bronx. Following his breakout season with the Rockies last year in which he finished with a 2.43 ERA, the righty put up a 1.90 ERA over 66 1/3 innings.

While Robertson was phenomenal down the stretch in '17, posting a 1.03 ERA in 30 outings after being reacquired at the Trade Deadline, he allowed five runs in five innings against the Astros in the ALCS.

CLOSER

Astros
Then: Ken Giles
Now: Roberto Osuna

Giles was solid in 2017, posting a 2.30 ERA and 34 saves in his 63 appearances. The postseason was a different story, with the right-hander allowing at least one run in six of his seven outings. That included yielding three runs on five hits and three walks in three innings against the Yankees. Houston allowed McCullers to pitch the final four innings of Game 7, locking down the 4-0 victory with four one-hit innings.

Osuna had a 2.63 ERA during the regular season and racked up an AL-best 38 saves. Yet with Osuna running into some trouble in Game 2 of the ALDS, it was Harris, not Osuna, who locked down Houston's first save of the postseason. Astros manager AJ Hinch insisted afterward that Osuna is the club's closer, but he certainly won't hesitate to turn to Harris with a game -- or the season -- on the line.

Yankees
Then and now: Aroldis Chapman

Chapman was even better this year than he was during his 2017 return to the Bronx. The flame-throwing righty posted a 2.21 ERA and struck out 85 hitters over 57 innings while recording 37 saves -- his most since saving a career-high 38 in back-to-back seasons in 2012-13. Chapman took the loss in Game 2 of the 2017 ALCS, when he allowed a walk-off double to Correa after entering at the start of the bottom of the ninth with the game tied 1-1. He bounced back to secure a save with a perfect inning in Game 4, his only other appearance in the series.

MANAGER

Astros
Then and now: AJ Hinch

Hinch led the Astros to the first of three consecutive 100-win seasons in 2017, and he continued that run this year with a franchise-best 107 victories. Under Hinch, the Astros this season became the first team in big league history that did not issue an intentional walk.

Yankees
Then: Joe Girardi
Now: Aaron Boone

The Yankees did not bring back Girardi, who led the Yankees to a World Series title in 2009, after their ‘17 ALCS loss. The Yanks have had back-to-back 100-win seasons under Boone, who kept them atop the AL East this season despite myriad injuries to major stars. Boone also famously described his hitters as “savages” during an epic argument with a home-plate umpire.