He told us all, didn't he? United's manager had long insisted - if his senior players were fit and available - their game would come together. And with Rapha Varane and Lisandro Martinez at centre-half. With Sofyan Amrabat, boasting a few more miles in his legs, anchoring the midfield. Ten Hag found himself a defensive base to build a game plan to rattle Manchester City.
"We knew if we closed the middle and allowed them to play from the outside it could get easier for us and knew the spaces were in behind them," declared Diogo Dalot afterwards. And that's just what the apex of Varane, Lisandro and Amrabat did. The latter outstanding as a defensive screen in front of the back four. Pep Guardiola, the City manager, would later admit the "man marking" of United was difficult for his players to overcome. And at the heart of that was Fiorentina loanee Amrabat. The Morocco international effectively taking Phil Foden out of the game with a performance which would've had Nobby Stiles beaming.
As Pep says, he wasn't ready for it, "We tried. We had clear chances in the second half which wasn't easy because they had man marking and defended the pockets..."
Just as Ten Hag caught Jurgen Klopp out with his use of Dalot in the triumph against Liverpool, the Dutchman was able to hatch another plan to outwit his opposite number.
It wasn't a performance for the ages. But it was certainly a result to be written into derby folklore. United gave as good as they received. City, as Pep says, had their chances, sure. But as did United and no neutral could claim those in Sky Blue were hard done by.
As we say, United benefited from having senior players available and playing in their favoured positions. Just as we witnessed last season before Lisandro's foot injury. You get that centre-half pairing together and United will always have a chance. It's like night and day.
Ten Hag can feel justified. He wasn't just whistling in the wind. Reaching for excuses. His players proved it at Wembley. Give him his first-choice central defence. Give him a decent holding midfielder. And his team comes together.
Is that enough for the board? For Sir Jim Ratcliffe? For this column, it should be. But for those in Ten Hag's corner, despite the achievement of Saturday, don't be assuming anything too soon.
Again, just as he did in the aftermath of the Liverpool thriller, Ratcliffe's silence on Ten Hag's future simply undermined him. A running check of this morning's red tops devoted equal coverage - if not more - of the final and speculation around Ten Hag's position. What should be a day to celebrate a landmark moment for the club. To end the season on such a high. And with all the promise and excitement it brings. Such reportage is given barely equal billing to Ten Hag's job and the prospect of this "project", as he describes it, being ripped up and started again.
Indeed, we had ridiculous situation of the defeated manager actually offering sympathy to his winning counterpart in what must be a first for any type of Cup final.
"They have to take a decision," stated Guardiola, as he - even in defeat - offered support to his colleague. "He's a lovely person and an extraordinary manager. Winning the FA Cup is important for them like last season it was for us."
Guardiola offering more to Ten Hag in that short soundbite than anything we've heard from United's chemicals billionaire. Ratcliffe did offer a reaction post-match, but failed to acknowledge the manager nor his players by name. And the way he warmly greeted Guardiola at the medals presentation compared to Ten Hag and his captain, Bruno Fernandes, does raise more questions.
For this column, as we've stated in recent weeks, Saturday's FA Cup boilover was achieved by Ten Hag, Fernandes et al, despite Ratcliffe, not because of him. The silence from United's co-owner, the lack of focused public praise for those responsible... all it does is take away from what was achieved and create a vacuum for speculation to run wild. And - finally - it seems we're not only ones to see it...
"Erik ten Hag has had to answer so many questions and he has certainly heard the reports this weekend," stated former England captain Alan Shearer. "On the day of the cup final he has had to deal with reporters asking about his future when all he wants to do is set his team up and get his team ready.
"From the human side of things, I don't think it has been handled at all well from Manchester United. If they are planning on keeping him, why haven't they come out and backed him beforehand?"
Saturday was a great day for Manchester United. As it was for Erik ten Hag. Give him the tools and he'll build a winning team. But whether that's to be at Old Trafford or elsewhere remains to be seen.
