Cardiff City learnt very quickly that there's a step up in class between the Championship and the Premier League. But manager Malky Mackay remains positive.
"We are here on merit. We won the Championship and we deserve to be here.
"For large periods of the game, I thought we were excellent and it is about making more right decisions than wrong.“It is day one and we have good belief in the dressing room. We are going to be OK”
"It's the next level up and you are going to be playing against players who are going to be more clinical, but I have good players in my dressing room."
Mackay, who is in this third season in charge at the Cardiff City Stadium, led his side to the League Cup final in 2012 and to the Championship title this year.
"We didn't start as well as we should, the first 10 and 15 minutes we started poorly and we had talked about how we were going to come out," he said.
"We played against a good team, in a nice stadium and in a great atmosphere and we didn't start well enough.
"Because of that they scored a good goal, but the half an hour before half-time we were excellent.
"We kept the ball and had possession in really good areas and we brought that into the second half.
"For vast periods of the second half we were on top and we limited them to three shots on target all day.
"But that being the case, it is about being clinical and we had a chance at the end and we stick it over the bar."
Joe Cole and Kevin Nolan scored the goals for West Ham as they showed their clinical ability to take chances when they were presented to them.
"This was never going to be an easy place to come, it never is," said Mackay.
"They defended very well and with numbers.
"They had a few great blocks from strikes we had, but we limited them to three chances on target at home.
"We defended well as a team, but we have to be more clinical."
The Cardiff manager gave debuts to two of their three major summer signings, defender Steven Caulker and midfielder Gary Medel, and was happy with their performances.
"They are what they are and I thought they were excellent," said Mackay.
"I have two top pros and international footballers and I thought they were both good."