NEW YORK -- Four years ago, the New York Yankees signed Masahiro Tanaka for this exact moment. To be the postseason ace of a World Series caliber team. They just didn't expect there to be so many bumps in the road along the way.

On Wednesday night, Tanaka's dominant October continued as he scattered three hits and one walk in seven shutout innings against the Astros in Game 5 of the ALCS. The Yankees won the game 5-0 and are one win away from clinching a spot in the World Series.

"He was special again," said Yankees manager Joe Girardi after Game 5. "You look at his three starts in the playoffs, they've been special."

In his three postseason starts, Tanaka has allowed two runs on 10 hits and three walks in 20 total innings, striking out 18. That includes seven shutout innings in Game 3 of the ALDS against the Indians, an elimination game win that spurred the Yankees on to their comeback from down 2-0.

"He's been doing it all postseason. Dominant. Just dominant," Todd Frazier said. "The ball just disappears on batters. I couldn't be more happy for him. He's a great guy on and off the field. Just what a performance. Gutsy. A big time win for him."

"That's what we expect out of him," Greg Bird added. "His last couple starts have been what he usually does. All his pitches were working tonight. Staying down in the zone. Every time you looked up, it was an 0-1 or 0-2 count. Didn't make any mistakes."

Tanaka's regular season -- and really his entire Yankees career -- has not gone as smoothly as the Yankees hoped. He missed the second half of the 2014 season with a partially torn elbow ligament, an injury he successfully rehabbed rather than undergo Tommy John surgery. 

Since then, the elbow seems to hang over every pitch Tanaka throws. He allowed a home run? It must be the elbow. He gave up a hit? Must be the elbow? A bad start? Elbow. Elbow elbow elbow.

Early in the 2017 season, there was a lot of elbow talk because Tanaka was legitimately one of the worst pitchers in baseball. He owned a 6.34 ERA through his first 14 starts and 76 2/3 innings -- that takes us through mid June -- and opponents were hitting .293/.342/.568 against him. Jose Abreu hit .304/.354/.552 this season, for reference.

At that point, after 14 miserable starts that had everyone wondering whether Tanaka's elbow was about to give, he made a change. He simply stopped throwing his fastball, his worst pitch. Not literally, of course. But he cut back on his fastball noticeably. From Brooks Baseball:

Masahiro Tanaka threw fewer and fewer fastballs as the season progressed. Brooks Baseball

The fastball usage went down and the number of breaking balls and offspeed pitches went up. Tanaka never got outs by overpowering hitters. He gets out by keeping them off-balance with his slider and splitter, his two best pitches. So he decided to start throwing them. A lot.

In his final 16 starts and 101 2/3 innings of the season, Tanaka pitched to a 3.54 ERA and limited hitters to a .227/.272/.384 batting line against. He went from facing nine Jose Abreus every night to facing nine Alcides Escobars (.250/.272/.357 in 2017). Tanaka has stuck with that approach in October.

"I feel like I'm just keeping it real simple," said Tanaka through an interpreter following Game 5. "You go out there and you fight and you empty the tank. I think I'm just really clear of what I need to do out there and I'm just executing that."

The Yankees went into the postseason with a legitimate ace: Luis Severino. The 23-year-old All-Star is going to finish in the top five of the AL Cy Young voting this year, and it was Severino, not Tanaka, who got the ball in the Wild Card Game. That start didn't go so well. Severino was knocked out in the first.

While Severino has since rebounded from the rough Wild Card Game, Tanaka has emerged as New York's best pitcher this postseason, throwing three gems to spur on his club's various series comebacks. This is the Tanaka the Yankees thought they were signing. A bona fide postseason ace capable of shutting down the best offenses, which he's done against the Indians and now twice against the Astros.

"I'm really glad how everything turned out," Tanaka added. "But I can't forget that it's not over yet. We'll see what happens moving forward, but I will start preparing myself for tomorrow."