LONDON -- Manchester United remain a baffling team to watch. Despite the confusion and disjointed play on Wednesday, United came away some impressive individual performances that led to three quality goals against a well-drilled Brentford side.

United's 3-1 win had its positive takeaways, which may hold a wider significance further down the line: the well-taken Anthony Elanga goal, Marcus Rashford breaking his goal drought, the growing influence of Fred in Ralf Rangnick's midfield, and the proof they can win a game without Cristiano Ronaldo scoring. But still, there are so many questions hovering over this team.

This was an important three points for Rangnick, after a stop-start beginning to his time in charge of Man United. He deployed a 4-3-3 after abandoning his preferred 4-2-2-2, but it finished with his squad playing three at the back as they held off a late Brentford fightback. The fact Ivan Toney's goal came from a corner will not have escaped Rangnick's attention. He will probably take note of the fact that United again failed to remotely trouble Brentford with their own set pieces.

Then there's Ronaldo, who did more to earn attention along the sideline than on the field. Having missed their 2-2 draw with Aston Villa on Saturday, Ronaldo was replaced after 71 minutes here at Brentford and looked disappointed to say the least. He was seen by the television cameras simmering on the steps near the Man United bench after having lost a wrestle with his coat, which was promptly thrown to the ground. While United celebrated their third goal through Rashford, Rangnick was seen deep in discussion with Ronaldo, explaining the decision to replace him.

"The only reaction I got from him, was him asking why me? I had to make the decision in the interest of the team," Rangnick explained after the match. "We were in the same situation as at the weekend -- 2-0 up and we didn't want to make the same mistake again. I decided to switch to a back five and it was the right decision. Cristiano was not happy -- he's a goal-scorer and would have wanted to score himself, but we needed the legs.

"I didn't expect him to hug me after being substituted," Ranknick added. "I know how those goal-scoring players think. I have no issues whatsoever with Cristiano."

That is a bit of that pantomime, which Rangnick will like. He'll be pleased to see some bite and anger in this United side from their star player, but for all of their second-half dominance and the eventual three points, this was far, far from a perfect performance from United.

Pre-match Rangnick called for his team to turn an impressive 70 minutes against Aston Villa at the weekend into a 90-minute all-court showing of physicality, mentally strong and at a tactically high level. Those hopes were a distant memory in the early throes of the match wherein Brentford were dominant.

The first-half for Manchester United was as bad as the second-half was good. Brentford comprehensively outplayed United in the first 45 minutes -- fashioning at least two chances for Mathias Jensen, which only the brilliance of David de Gea kept out. United scrambled and, while they chased the ball with gusto, they left themselves positionally bereft and Brentford exploited that through the counter-attacking ability of Bryan Mbuemo. United held on for 0-0 at the break, thanks primarily to De Gea -- a familiar narrative, to be sure.

"I am unbelievably proud of the team and the players," Brentford manager Thomas Frank said. "The way we absolutely destroyed them in the first half was impressive - we had 6 chances, they had zero. It's a miracle that they weren't 2-0 down at half-time. De Gea was by far the best Man United player today."

Rangnick apparently agreed with that assessment of De Gea, telling reporters afterward: "We have to be honest, without David and his brilliant saves, it'd have been difficult to keep a clean sheet at half-time. We were second best in all aspects of the game in the first half, sloppy passing, losing 50/50 situations and we didn't win a second ball in the first half."

But then came a different, angrier beast in the second half and a shift in style. Man United worked out how to play a transitional game with greater efficiency, and it produced three well-taken goals. They attacked through the middle and targeted the half space, rather than down the flanks. The piercing runs of Fred and Scott McTominay caused Brentford difficulties, the diagonal balls started finding their targets and from that came opportunity.

"In the second half we did a lot of things a lot better, in the end we could have scored four or five goals," Rangnick said."

Brentford saw the ominous signs of Man United's pretty much immediately after the break as Ronaldo floated a header on to the bar. Then came the breakthrough after 55 minutes as a neat through-ball from Fred found Elanga, who hooked the ball up to head it home himself past Jonas Lossl. The second goal, seven minutes later, was a wonderful sweeping move as Ronaldo chested the ball into Bruno Fernandes' direction, who countered and found Mason Greenwood unmarked to tap it home for 2-0.

This triggered Rangnick's switch from a 4-3-3 to effectively a back five, and from that United kept their hold of the match with Rashford landing a key third goal -- a well-taken near post effort in the 77th minute after Fernandes put it on a plate. It was Rashford's first in 11 games and he will hope it triggers the start of a run of form for the England forward.

There remain cracks in United's foundation and unanswered questions. Anthony Martial's immediate future remains uncertain as he cut an isolated figure on their bench, an unused substitute. Then there are their troubles from set pieces: United looked vulnerable at the back, while the running tally of 113 corners without a goal remains a real issue.

Eric Ramsey, the set piece coach, was seen madly flicking through his iPad in the early stages of the match, analysing Brentford's threat from long throws, and analysing the corners. Man United still look extremely vulnerable to counter attacks, and their scrambling defence can be picked apart with ease.

This was a case of job done for United, winning a match that could have been out of reach by the break had it not been for De Gea. Rangnick will be delighted with their well-taken, three second-half goals, but this was far from convincing as we wait for a United to emerge capable of putting together a 90-minute performance.