Cardiff City manager Malky Mackay was frustrated by his side's slow start in their 2-0 defeat to West Ham on Saturday.
An early goal from Joe Cole set the home side on their way at Upton Park, before Kevin Nolan's effort in the second half wrapped up a routine win for Sam Allardyce's side.
And Mackay believes his squad's hesitancy in the opening exchanges cost them dearly on their debut Premier League outing.
"I thought we started the first 15 to 20 minutes slowly. We knew we had to start better than we did and in that first 15 minutes they were clinical with their finishing," he said.
"After that, in the last half an hour of the first half I thought we had plenty of possession without any penetration.
"The second goal again was clinical. We had one really good chance in the second half, as they did, but they scored theirs and we didn't score ours so it's learning as far as that's concerned."
Mackay also insisted his team must improve their decision making if they are to fare better in the top flight this season.
"Overall I can't be too harsh on my players because on a day at Upton Park I thought we had an awful lot of posession and gave a good account of ourselves," he continued.
"It needs to be better but we're away from home against a good team. They were clinical with their two finishes and we weren't.
"I don't think it's a lesson because we knew before that we had to be clinical, it's about choices and that final pass."
Cardiff face the daunting task of hosting Manchester City in their next game.