Lisandro Martinez insisted Manchester United only had themselves to blame for the 2-1 defeat at West Ham.
Jarrod Bowen scored a controversial stoppage-time penalty, after a VAR review adjudged Matthijs de Ligt had fouled Danny Ings, to send United spinning to a fourth Premier League loss in nine matches this season.
But the Red Devils missed a host of chances to score before Casemiro’s header cancelled out Crysencio Summerville’s opener for West Ham.
Alejandro Garnacho hit the crossbar and put a good chance wide, Bruno Fernandes headed over and Rasmus Hojlund and Marcus Rashford also missed presentable opportunities.
But the chief culprit was Diogo Dalot, who rounded Hammers goalkeeper Lukasz Fabianski before blazing wide of an open goal from 12 yards.
The defeat saw United slip to 14th in the table, cranking up the pressure on boss Erik ten Hag, and Argentina defender Martinez admitted it was difficult to accept.
“I am feeling very disappointed,” the 26-year-old told MUTV.
“I hate to lose and I hated losing that, and in this club it is not what we want. The expectation is really high for sure and we want to win every game.
“But now it is time to accept it and be honest with ourselves and keep going.
“I want the best for this club. I am pretty sure that this club will be at the top. We will give everything to put this club where it deserves.
“I am so frustrated, honestly, because I see every day our skills, our quality, and then those days that we finish a game, we lose, we miss many chances and it is difficult to accept it, but we have to accept it. That is it.
“Everyone fights and we give everything, but I think we have to give more.
“We have to know that in football it is a mental game and we have to keep believing and believe until the end and be hungry.
“We played very well in the first half, but in the second half we dropped. We conceded the two goals and we could not win the game. I am so disappointed, honestly.”
Summerville, a half-time substitute, ran to the dugout to celebrate his first goal for the club with Mohammed Kudus, who is suspended following his red card meltdown at Tottenham last weekend.
“I told Mo that when I came on I was going to score,” said the summer signing from Leeds.
“I’ve had to be patient at times so far this season, but when I come on I just try to give energy to the team. I think that’s why West Ham wanted me.”