He will be relieved, of course, to get his first competitive win since arriving from Ajax Amsterdam this summer and delighted to have done it against an archrival in a big game, one that a saw large group of Manchester United supporters protest the Glazers' ownership.
Instead, Monday's 2-1 victory over Liverpool also will be remembered -- perhaps just as importantly -- as the night the Dutch manager put his stamp on the squad.
In dropping Cristiano Ronaldo and Harry Maguire for arguably the biggest game of the season, Ten Hag gave notice to his players that he is in charge. After a demoralising start that briefly saw United fall to the bottom of the Premier League table, victory over Liverpool will do everything for the confidence and self-belief in a dressing room that looked at rock bottom following the 4-0 defeat to Brentford nine days earlier. But it could be the team selection that ends up having a far bigger impact.
Ten Hag spent the summer ruling with a quiet authority but picked his moment to show his teeth. You can't get much more ruthless than benching your star striker and club captain (with Bruno Fernandes instead wearing the armband) against Liverpool at home.
"I have a squad, and we have to use the squad," Ten Hag said afterward. "We play 50 or 60 games, and from game to game, we will see what team we will pick. I don't have to mention Maguire and Ronaldo; they are amazing players, and they will play a role in the future and the short-term future, as well.
"We have a squad and a way of play, of style, but also a game plan. You look at what's the best approach for the game. We need a squad because we have many games to cover, so we make a team out of the squad, we stick together as a squad and we achieve a lot. I'm confident about that."
It is understandable that Ten Hag would want to play down the significance of benching two of his highest-profile players for such a key game, but he will know better than anyone that it sends a strong message to his squad very early in his reign. He made his feelings clear after the defeat at Brentford, accusing his players of a lack of "hunger" and cancelling a planned day off so they could make up the distance by which they had been outrun by Thomas Frank's side.
Ten Hag resisted the temptation to single out those he felt were most culpable, saying only that he wished he could have made 11 substitutions at half-time. But when it came to picking his team against Liverpool, he didn't shy away from the big decisions.
He could have left out Lisandro Martinez -- replaced after 45 minutes at Brentford -- pushed the Argentine defender into midfield, or switched to a back five with three centre-backs. Instead, he dropped Maguire, his captain. Already well aware of the constant noise around Ronaldo, the easy decision would have been to keep the 37-year-old in the team, but instead, he was handed a seat on the bench behind Maguire.
It was telling too that when Anthony Elanga was substituted at half-time, it was Anthony Martial, rather than Ronaldo, who was sent on in his place. Ronaldo eventually came on with only four minutes left, but his introduction at the same time as that of Donny van de Beek and Aaron Wan-Bissaka was little more than an afterthought as Ten Hag tried to see out the final stages of the win.
Maguire, meanwhile, barely even warmed up and spent the night watching from the sidelines. He is unlikely to get back in for the trip to Southampton on Saturday, after Martinez and Raphael Varane defended with such resilience against Mohamed Salah, Roberto Firmino and Luis Diaz.
Ronaldo won't be expecting a recall at St Mary's, either, after contributing one shot toward goal that sailed into the Stretford End. It felt pointed too that afterward Ten Hag stressed the importance of "leadership" on the pitch despite playing without his captain and most experienced player.
"I wanted a different approach and a different attitude, and that is what they brought on the pitch," Ten Hag added. "Be a team and have a good spirit, and that is what we saw today. It is not always about what I said. I said we have to act and not to talk a lot and make sure you are a team and battle and be brave and give each other options.
"Fernandes took the responsibility, and the captaincy encouraged him. He showed leadership with Varane. They made a huge difference. It is not just them; we need more leaders. When you want to win, you need leaders and the spirit we showed today."
Ten Hag's decisions will do nothing to dampen the speculation around Ronaldo's future, while there also have been reports of interest in Maguire from Chelsea. Ronaldo could find his path back into the team further complicated if United are successful in their efforts to sign a winger -- Ajax's Antony, Chelsea's Christian Pulisic or PSV's Cody Gakpo among those reportedly considered -- before the transfer deadline, although Ten Hag maintains the Portugal forward remains part of his plans.
Whether Ronaldo wants to be part of those plans remains up for debate, but if nothing else, Ten Hag has shown that it's Ronaldo who will have to adapt to his manager and not the other way around. United fans have believed for a while that there has been a lack of accountability among the players, that they have regularly been able to turn in miserable performances over the past 18 months without seeing consequences when the team was announced for the next game.
For now, at least, the cycle has been broken, and while Ten Hag has eased some of the pressure on himself, he also has made sure his players are reminded there is plenty of pressure on their places.