One of the coach-speak tenets in every sport is not to look ahead, not to look past the opponent, to focus on the task at hand and not waver from that.

But the eyes of the Red Bulls players and their coach, Jesse Marsch, are unabashedly fixated on the prize at the end of the playoff rainbow: the MLS Cup.

This is the only thing on the minds of the Red Bulls as they play the Montreal Impact in first leg of the MLS Eastern Conference semifinal Sunday at Stade Saputo. The teams will meet again next Sunday at Red Bull Arena.

The Red Bulls, who finished first in the Eastern Conference and are the No. 1 seed, have accomplished virtually everything there is to accomplish in the league in the last four years.

They have won the Supporters Shield as the top regular-season team twice (in 2013 and 2015). Their top striker, Bradley Wright-Phillips, won the Golden Boot by scoring the most goals for the second time in three seasons. Their goalkeeper, Luis Robles, owns the league ironman record for most consecutive games played and has become one of the best net minders in MLS.

The Red Bulls, as a team and individually, have basked in varying degrees of excellence for years, this being the seventh consecutive season they are in the playoffs. But one thing remains missing: an MLS Cup.

The Red Bulls — particularly the veterans like Robles, Wright-Phillips and midfielder Dax McCarty — burn to lift that elusive cup for the first time, and they are not shy about stating their desire.

“I’m not afraid to acknowledge the fact that our goal right now is to win MLS Cup,” Marsch told The Post. “To honor everything that’s been done here — because there’s something genuinely unique and special about what this club has become — we have to win the Cup. We have to. It’s not that we want to. It’s not that that’s our goal. We have to do it. Because that’s the exclamation point to show this is what we are.”

When it was suggested to Marsch this might ramp up the pressure on his team, he did not flinch.

“It’s our reality,’’ Marsch said. “This is our world right now, and we’re focused in on it. Will I only consider this season a success if we win the Cup? Yes. Yes. We have to win the Cup. But that’s not pressure, that’s our reality. That’s where we’ve put ourselves in that we’ve created that conversation and now we have to finish it off.”

The Red Bulls have come tantalizingly close to finishing it off. In 2014, they were edged out by New England on aggregate goals in the Eastern Conference final. Last season, they were eliminated by Columbus in the Eastern Conference final, 2-1 on aggregate.

“Dax, Bradley and myself were on the field for the 2013 Supporters Shield and when we got kicked out of the playoffs, it just left this bitterness in our mouths,” Robles said. “Yes, we got the first piece of silverware for this organization [the Supporters Shield]. Yet at the end of the day, there was this void. And that void is not being able to win the MLS Cup.

“So 2014 comes around and we’re so close it’s right there in New England and then unfortunately we gave that goal away at the end. And then in 2015 we won the Shield and again so close.

“The three of us have been able to experience a bunch of personal success, we’ve seen this team experience success that it had never experienced, and yet that void continues to exist,” Robles added. “In the American sports culture landscape, you have to win the MLS Cup. In America, we have the playoffs and the playoffs are the end-all, be-all.

“The fact that you have to explain to someone what the Presidents Cup [in the NHL] or the Supporters Shield is says a lot.”

Wright-Phillips, who scored a league-high 24 goals this season and has 68 in the last three seasons, called the MLS Cup “everything to me … and we haven’t done that yet here.”

“With us, it’s hard to envision wining the Cup because we’ve never physically lifted it, so it’s hard to know you’re doing the right thing,’’ Wright-Phillips said. “If we win it once with how we play, we’ll have that recipe of how to win it a lot more times. It’s just getting over the first hurdle.”

Penalty Kicks

The Red Bulls are the hottest team in the league, unbeaten in their last 16 matches (9-0-7). The Red Bulls and Montreal have met three times this year, with the Impact winning one at home the Red Bulls winning twice at home. The Red Bulls lead the all-time series 8-3-2.

Holding second-half leads has been a problem for the Red Bulls, having blown five of them in a 10-game span to turn wins into draws and leaving 10 points on the table. “It’s always going to be a challenge when you have the lead and teams are going to throw a lot at you in the end,’’ coach Jesse Marsch said. “I think we’ve learned from it and I think we’re better for it and I think we’ll be more prepared when it comes up again.’’

The key player for Montreal is Argentine midfielder Ignacio Piatti, who can be a magician of a playmaker. “When you are talking about dealing with [Montreal], you are talking about dealing with Piatti, him being on the move and transition,” Marsch said. “But we have had good success against them when we are able to still possess the ball, play in their end, be aggressive.’’