The Red Devils have won both of their Premier League fixtures under the German coach by a 1-0 score, beating Crystal Palace at home and coming through a stiff examination away to Norwich on Saturday.
United were hit by a “small number” of positive Covid-19 lateral flow tests results on Sunday but the clash in west London remains on with the visitors aiming to keep a third clean sheet in a row in the division.
Asked about the importance of another shut-out, Rangnick, speaking after the victory at Carrow Road, said: “It can only be achieved as a whole team. It is not only the back four, the goalkeeper and the two sixes.
“The whole team has to defend in unison together and as I said so far we had two clean sheets in the league. We win 1-0 again in a difficult game.
“We tend to call those games the dirty away wins, 1-0. Those normally are the nicest ones but in the second half, in my opinion, we just conceded too many corner kicks and free kicks from the side.
“So therefore until the last minute it was a game that could have gone in the other direction and we needed a fantastic goalkeeper, a few headers in the centre of defence to keep the clean sheet.”
United had pressed with good intensity during Rangnick’s first match against Palace but that was largely non-existent last weekend.
While the experienced manager put it down to the performance of the opposition, he wants to see more from his players in London.
Rangnick added: “We need to take next steps. It is about taking next steps and it is easier to take those if you are winning games.
Now we need to try and raise the level of how we play with the ball up front
“In defence, the centre-backs and two sixes did extremely well. Now we need to try and raise the level of how we play with the ball up front.”
The former RB Leipzig boss watched Brentford’s 2-1 win over Watford on Friday and is predicting another full throttle encounter.
Given the quick turnaround from the trip to Norfolk, changes could be made with Luke Shaw on the bench at Norwich while Aaron Wan-Bissaka and Edinson Cavani were set to return after their respective injury issues.
“I saw the game of Brentford against Watford. Again, another high-intensity team,” the United interim manager admitted.
“Maybe even more physical than how Norwich played and we need to be aware and prepared for that different level of intensity.
“We have to wait and see (over making changes). A few players are available again, like Luke Shaw, who was on the bench. Maybe Aaron Wan-Bissaka will be available and even Edi might be an option but we have to wait and see.”
United will have to assess Victor Lindelof after he was forced off against Norwich due to breathing difficulties although Rangnick did reveal post-match the Swedish defender was doing “okay” after club doctors had checked him.
One player definitely not expected to be at Brentford is Anthony Martial, who continues to struggle with a knee injury.
Martial’s agent also made comments over the weekend about his client seeking a move away from Old Trafford.
But Rangnick said: “If he has a wish to go to another club, it should be the player who informs either the board or myself.
“I don’t communicate with agents via the media and the press. The player hasn’t spoken with me or us about it.
“After the final training session before the Crystal Palace game, after having trained with the team, he informed the doctor and medical staff he would not be available because the pain on his knee is too big, so we have to wait and see with Anthony.
“To be honest what his agent says via media is not that much of interest to me.”