1) United's wingless wonders were better out wide
Manchester United started this game at Watford like the Brazilian team of 1982. Safe in the knowledge that Paolo Rossi was unlikely to turn up and net a hat-trick against them, United began in an unusual 4-2-2-2 formation, forced upon them by the absence of Anthony Martial and Wayne Rooney.
Memphis Depay and Jesse Lingard shared the load up front, with Ander Herrera and Juan Mata playing in behind them. True, Herrera and Mata may not quite be on the same level as Socrates and Zico, and United's approach was not quite as naively cavalier as the 4-2-2-2 of that famous Brazilian World Cup side of 33 years ago, but it worked as they got on top early in the game and took the lead through Depay's volley.
United's complete lack of experienced attacking options on the bench did however mean that once Herrera went off injured after 25 minutes, Louis van Gaal felt he could not persist with the formation - opting to bring on Marcos Rojo as a third centre-back in a 3-4-1-2.
Both formations were a departure from the 4-2-3-1 they have generally preferred in recent times, and it appeared to give them more purpose in attack, showing they can be a little more entertaining than they have been on some occasions recently - and still win.
Before this game they'd attempted only 85 shots in 12 games this season, excluding blocked shots, at just over 7 attempts per match. Sunderland were the only Premier League side who had attempted less. The figure was as low as 3 in their last away match at Crystal Palace but in this game they had 13 attempts, of which 2 were blocked.
With two livewires up front, United's tempo was higher and they were less prone to tedious passing without any real purpose in midfield - something that was particularly noticeable in the 0-0 draw at Selhurst Park. In total they completed 377 passes against Watford, only two more than at Palace, but 122 of them were in the attacking third compared to just 87 against the Eagles.
Perhaps most intriguingly, despite doing away with wingers at Vicarage Road they were also more effective out wide - completing 8 crosses, compared to 3 in each of their past two Premier League matches, when the likes of Anthony Martial and Juan Mata preferred to cut inside rather than look to put the ball into the box. Both of United's goals against Watford came from crosses in some way, with Depay's goal from a particularly impressive centre from Herrera.
United had been accused of being dull to watch in their previous 4-2-3-1 system, although Van Gaal did point out that his side kept possession better in that formation. Their pass completion rate at Watford was 76.3%, compared to 83.3% and 82.2% in their previous two league matches.
"Our possession play was not so good, I changed the shape because of the injuries in the attacking positions and maybe it was because of that," Van Gaal said.
"But we created a lot of chances and we could have finished the game much earlier. We only trained once in that system and also we changed during the match to three defenders, the system we played for three or four months last season.
"We have to improve our possession game, in other games we were very good - so good it was boring, I read. But it's a way to disorganise the opponents."
2) Memphis flourishes up front
Manchester United's number seven shirt has been worn by some pretty special players in the past, with away fans taking the opportunity to sing about Eric Cantona during the pre-match rendition of La Marseillaise. Memphis Depay has struggled to impress in quite the same way since arriving in England but was recalled to the starting line-up at Vicarage Road with Martial and Rooney unavailable.
Memphis has largely operated on the left since joining United but in this game he played in a more unfamiliar position up front - a position where he laboured unconvincingly for much of the Netherlands' crucial home loss to Iceland in September. For United though he flourished in a more central role, where he had more space to operate and less chance to run down blind alleys out wide.
He produced a fine finish for his goal and in total managed an impressive 4 attempts, as well as creating a chance that Lingard might have done better with. He also occasionally drifted back to the left to attempt 4 crosses, and completed 19 passes in the attacking third - a total only equalled by Juan Mata. His pressing without the ball was good too, as Watford boss Quique Sanchez Flores noted afterwards.
Van Gaal also praised the Dutchman, saying: "He finished his goal very well and in the first half he played a very good game. In the second half he wasn't as good because he's been out of the team six weeks so he lacked some rhythm, I can understand that. But he played a very good game and the way we played suits him and Jesse Lingard. That's good because now we know he can also play in another system."
3) United fare better without Rooney
Wayne Rooney missed this game because of illness but Manchester United have actually done better without him in recent times, perhaps a sign of his waning influence at Old Trafford. United have taken 81 points from the last 43 league games that Rooney has featured in, at 1.88 points per game. Without him, they have won 5, drawn 4 and lost none (2.11 points per game).
Rooney can no longer always provide the youthful energy that the likes of Jesse Lingard and Memphis Depay brought up front, with Lingard again proving lively in this game. The 22-year-old needs to improve his finishing but had 3 shots and completed 13 passes in the attacking third - Rooney completed only 5 in the last away game at Crystal Palace.
4) Young and Blind played crucial roles
Playing without wingers put greater emphasis on United's full backs, or wing backs as Ashley Young and Daley Blind became following the introduction of third centre back Marcos Rojo.
The pair both stepped up to the plate by getting forward well, particularly in the first half, and providing the width that United could have been badly lacking without them. The fact that Young is a natural winger undoubtedly helps, while Blind completed 49 passes - more than anyone in the field, with 13 of them coming in the attacking third.
Young attempted 6 take-ons, even if only 2 were successful, while he also fared well in the ball recoveries stats with 12. Only Morgan Schneiderlin (13) completed more, while Blind wasn't far behind with 11.
5) Ake improved things for Watford
Quique Sanchez Flores admitted he was not happy with his side's first half performance, and they completed only 62.4% of their passes before the interval. But he was much happier with how they fared after he introduced Nathan Ake at half time for Jose Manuel Jurado. Ake came on at left back with Ikechi Anya moving to the wing, and Watford were the better side for a period, having 7 shots to United's 6 before half time and their equaliser.
David De Gea made some good saves but Watford got their goal, ending United's run of 642 minutes without conceding a goal in all competitions - and thwarting their hopes of a sixth consecutive clean sheet for the first time since 2005.
Despite only coming on at half time, left out after being away on international duty with the Dutch under-21s last week, on-loan Chelsea man Ake completed more tackles in the game than anyone, winning 6 out of 6.