Sacha Kljestan:  “We’ve got to be better going into their place.”(Brad Penner/USA TODAY Sports)

By Michael Lewis

FrontRowSoccer.com Editor

PURCHASE, N.Y. — The latest edition of the Hudson River Derby can be defined by the number four.

That number played prominently in the latest results of the two rivals last weekend, with the Red Bulls rolling to a 4-0 triumph over the Montreal Impact Saturday and while New York City FC was routed by Toronto FC by the same score Sunday.

And then there are the last four games each team has played.

The fourth-place Red Bulls (11-8-2, 35 points) are 4-0 and breathing down the necks of NYCFC (11-7-4, 37), which has stumbled to a 1-2-1 mark.

One team hopes to continue its run while the other tries to rediscover itself and rhythm in Sunday’s 6 p.m. at Yankee Stadium.

Since the last time these two teams met, the Red Bulls have been at the top of their game, outscoring their opponents, 12-1, in their past four matches. And winning all six of their games — two in the Lamar Hunt/U.S. Open Cup — since they defeated City in the Open Cup, 1-0, June 24.

“Ever since that game we’ve made a few changes and we’ve been on very good run here,” Red Bulls captain Sacha Kljestan said. “So we hope to keep our good run of form going hopefully go into their place and come out with a positive result.”

Added midfielder Daniel Royer, who has scored six goals in those four games: “We have to continue playing like the past weeks. I’m quite confident that we’ll make a good game and we’re going to get a good result.”

NYCFC, having played the cream of the Eastern Conference in three of those four matches, Toronto FC twice and the Chicago Fire once, is struggling to find its rhythm and game.

“We have a good rivalry against them,” City forward Jack Harrison said. “We always have good games against them. We want to redeem ourselves as well. Every time we get set back, we want to have a good response. Looking to do that this weekend.”

NYCFC head coach Patrick Vieira hoped that Sunday’s encounter will be similar to the June 24 result.

“Playing at home is a huge advantage, and we managed to win over there,” he said. “We played a really good game, I would say nearly a perfect one. If we want to win this game, we need to be at our very best.

“All the games will be really difficult, especially the derby ones, so if we want to take those three points we have to work really hard and we have to play much better than we did against Toronto.”

His Red Bulls counterpart, Jesse March, isn’t taking anything for granted, though his team has forged a 6-2-0 record against City. That included a 2-0 NYCFC win at Red Bull Arena June 14, which helped turn the Red Bulls’ season around.

“That game they played with more desire, with more physicality and heart,” he said. “We’re not happy about that result. It would be really important for us to find a way to get a result. Our guys will be up for it. Their guys will be up for it. They’re disappointed with their last game, I’m sure. It sets up for a very interesting matchup.”

Subtract the fact that this is a rivalry and this encounter is an important game because the teams are so close in the standings.

“The most important thing to me, derby aside, it’s a game that keeps us where we need to be in the chase for what we want to achieve this season,” NYCFC goalkeeper Sean Johnson said. “Obviously, two good teams stepping on the field and it’s going to be a battle. It’s a cross-city derby. It’s also two teams that are close. That’s the most important thing. To answer a question that was posed to me in Chicago, in the aspects of the emotion of the match and this is same … for this game.”

Since the last time these two sides met, the Red Bulls have changed their formation to a 3-3-3-1 and the team has been difficult to beat.

“The system is a way to set up the team,” Vieira said. “If you look at the way they are closing people down, that didn’t change. This is a team that has a lot of energy, working really hard for each other. They have a strong collective game around the box. This is the reason why they’ve scored the goals. I don’t think the system will matter, really, because the philosophy doesn’t change. That is a why I believe it will be a difficult game. One of the reasons is that they are in a really good period and they are having a really good momentum with a lot of confidence.”

That’s what the Red Bulls hope to continue Sunday.

“We beat them in the Open Cup, which has been big for our season,” Kljestan said. “It was good kick start for us. The loss pushed us to make some changes. We need to come in with a much better mentality. The physical part of the game during the 2-0 loss was not good enough from us. They were very combative. To be fair they were better on that day and deserved to win. So, we’ve got to be better going into their place.”