Manchester United had put together a decent run of form to suggest that they were in with a chance of chasing down fifth place, even if a Champions League spot looked unlikely with so few games remaining.
However the club suffered a blow in midweek with an injury to in-form striker Rasmus Hojlund, who could also miss the Manchester derby next week.
That led to teenager Omari Forson being given his first start for the club against Fulham on Saturday, with Alejandro Garnacho and Marcus Rashford filling out the front three, as Anthony Martial was out injured, and Antony remained on the bench as he continues to struggle for form.
The game was goalless at the halfway point but the away side had the better chances, and they broke the deadlock midway through the second half through Calvin Bassey.
Harry Maguire scored an 89th minute equaliser, but Alex Iwobi struck in the 97th minute to claim all three points for Fulham.
Speaking after the match, Ten Hag was disappointed with the manner they conceded the second goal, saying: "It was a throw-in [for Fulham] in the corner, we had them under pressure and we have one player in the wrong position.
"As a team we should manage that and make sure everyone is in the right position. We let them escape and it is avoidable.
"The team showed big character to fight back, we deserved the equaliser and went for the win - we showed big personality and character. It was that mistake. Before that we went for the win and we should have taken our opportunities.”
He hinted United were missing the injured Luke Shaw, adding: "We struggled with their influence and their impact on our left side. But we reacted well and how to deal with it, how to step up from the back and once we had that we got more from the game and took control to create the chances.
“With the squad we had today we should have won this game. Both halves were slow starts and we should be ready from the first whistle.
"That's a point of criticism but the team showed big character in both halves."
United defender Maguire added: "Overall on the balance of play we didn't do enough in the first 60 minutes or so, we started the game not great.
"The first half was pretty even, but when you're not playing at your best you have to do the basics right and set pieces are part of that.
"We knew they would cause us a threat from those areas and they scored early in the second from what we knew - so that's disappointing on that aspect.
"To be a goal behind, I thought our reaction was brilliant especially in the last 30 minutes and when we equalised probably only one team was going to win it.
"We were probably naive in the end by throwing too many bodies forward and getting done on the counter attack.
"We've been on a good run of form and came into the game we were confident."
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