Joey O'Brien admitted to having mixed emotions following his West Ham United debut.
The Hammers' new No17 enjoyed an impressive debut at right-back, only for his day to be ruined when Kenny Miller's last-gasp strike scored a 1-0 npower Championship victory for visitors Cardiff City.
The Irishman defended stoutly and also got forward to good effect on a number of occasions - most notably when he jinked his way to the by-line before setting up a gilt-edged chance for Freddie Sears.
Speaking to West Ham TV, the 25-year-old admitted the home side should have taken the opportunities they created.
"I think we had enough chances to win two or three games, but we committed the cardinal sin at the back of letting them score with what was only their first or second chance of the game," said O'Brien.
"It was a killer blow for the whole team. We should have got a minimum of a point from the way that we played, but it was not to be, but the performance was really good I thought."
The Republic of Ireland international was one of three West Ham debutants alongside captain Kevin Nolan and Matt Taylor, but the home side looked far from strangers as they produced a series of fine attacking moves.
"I felt that we came out of the traps really well early doors. We had chances and the tempo and the atmosphere helped as well. I felt for the majority of the game we looked really good.
"The atmosphere was fantastic. I've always loved coming here with Bolton, listening to the fans on the way out. I thought they were really good for us today."
While the support for the team was second-to-none, O'Brien conceded that West Ham would have to up their collective game if they are to get their promotion bid back on track at Doncaster Rovers on Saturday.
"When teams play against West Ham they are all up for it. You could see when Cardiff scored the way they celebrated was as if they had won the league.
"That is the way it is going to be with teams this season, especially when they come to Upton Park, they really want to take the scalp of West Ham United.
"So as a football team we know that as well as anyone, so we have to start getting points on the board.
"I think the way we started the game shows that we can work hard. Some of our players haven't been in this situation, but when you look at Kevin Nolan, he had exactly the same situation with Newcastle and they went up. He knows this level and what it takes to get promoted and so hopefully he can lead us which I'm sure he will."
While O'Brien is convinced of Nolan's leadership qualities, he is also happy with his own level of fitness after three years blighted by a serious knee injury.
"I think I'm still a bit off match-fitness wise. Towards the end I was feeling it a bit, but I think I just need to play regular games. I haven't played a lot of games in the last three years really, so if I can get a run of games in the next five or six weeks, I will feel the better for it."