Manchester United against Tottenham is a meeting of two sides that keep winning the territory battle and getting little back for it, so I'd look at the first goal rather than at who has the better squad. United are 12th with one league win from five, Tottenham 20th with no win and two goals scored. Both lean on volume (United's 29 shots at Fulham, Tottenham's 20 against Aston Villa), and in both cases the volume has not been the same thing as control of the result.
United first, from the match records in our DB. At Fulham they had 29 shots to 12 and 58% of the ball, but 12 of those shots were from outside the box and the xG was level, 1.60 to 1.62. They trailed after an own goal in the 63rd minute and only equalised in the 89th. Against Manchester City at home it was 16 shots to 6, yet they lost 0-1 even though City were down to ten men from the 23rd minute, and United's xG was 1.00 against 1.10. In the cup against Brighton they were 2-0 up by the 10th minute and lost 2-3. So the pattern is not that they cannot create, it is that early or late swings keep deciding games they were running.
Tottenham's version is quieter. Against Villa they had 64% of the ball and 20 shots to 15, xG 1.56 to 1.16, but were 0-1 down at the break, 0-2 by the 67th and 0-3 by the 79th, and their two goals came in the 86th minute and in the eighth minute of stoppage time. The Everton game finished 0-0 with 62% possession, but xG there was only 0.69 against 1.11. In the cup at Liverpool their xG was 2.42 to 1.82 and they still lost 1-3, with the decisive goal in the 91st minute. They are not being outplayed, they are not finishing the moments that matter, and they are conceding first.
That is why I'd read the opening hour as a test of who gets to be the team in front. If United score first, Tottenham's habit of chasing from behind meets a United side that has not shown it can protect a lead (Brighton). If Tottenham get the first goal, they have barely done that this season, so it would be a new situation for them too. Our availability data also lists Sesko and Mainoo as doubtful for United this morning, and Kulusevski, Odobert and Simons as confirmed out for Tottenham, so the pieces that usually settle those scrappy phases may not be the usual ones. I'd treat all of that as unconfirmed until the lineups are out.