With the forecast calling for rain much of the day in The Bronx on Wednesday, Major League Baseball could postpone Game 4 of the ALCS between the Yankees and Astros by noon — moving the game to Thursday, which would push Game 5 to Friday at Yankee Stadium.

And it could significantly alter the Yankees’ pitching plans.

If it is a washout, the Yankees could go from using an opener on Wednesday to going back to Masahiro Tanaka on Thursday Game 4 on full rest — and Houston could go back to Zack Greinke.

It would also make a huge difference with the Yankees’ bullpen, because the series would lose Friday’s off day — meaning the teams would play four games in four days if the series goes seven games.

Chad Green, who may be used as an opener if Game 4 is played Wednesday, threw just eight pitches in Tuesday’s 4-1 Game 3 loss. And he said the bullpen was ready for the added workload — even though the Yankees have been especially careful about not letting their relievers pitch on even three straight days.

“I think you know might have to pitch in every game,’’ Green said. “At this time of year, you just do it. That’s the only mindset to take. You can’t worry about ‘I threw X many days in a row.’ You take the ball when your name is called and see what happens.’’

That’s MLB’s policy regarding the weather heading into Wednesday.

“We’re watching the forecast,’’ MLB commissioner Rob Manfred said before Tuesday’s game. “We’re mindful of two things: We don’t want to affect the competitive complexion of the series and we want to be mindful of our fans who’ve got to get out. We don’t want to bring them here if we know we’re not gonna be able to play.”

Thursday’s game is scheduled to begin at 8:08 p.m. If it’s moved to Friday, it would likely be either at 4:08 p.m. or 8:08 p.m.

Fans with tickets to Game 4 will be able to use them for Game 4, whether the game is played Wednesday or Thursday.

The same is true for fans with tickets to Game 5, regardless of when the game is played.

What’s less clear is how a potential rainout might impact both teams.

Game 2 starters James Paxton and Justin Verlander would be in a similar situation as Tanaka and Greinke for Game 5. And with the loss of the scheduled off day Friday, the teams could instead go the bullpen route on Saturday for Game 6 before Luis Severino and Gerrit Cole would be on regular rest again for a possible Game 7 on Sunday in Houston.

The Astros can expect more length out of some of their starters — especially Verlander and Cole — and would therefore be less impacted by the shift.