The Dutch club were 1-0 up at half-time at the London Stadium in the first leg but were outplayed in the second half as West Ham came back to win 2-1.

AZ coach Pascal Jansen felt his side did not take advantage of a “vulnerable” West Ham.

“We have to learn to make better use of opportunities that come our way," said Jansen.

"When you hear the stadium raging against their own team, there are more options. But then we have to be more clinical in West Ham's half. That's the challenge for next week.”

Home supporters were certainly not happy at the break after Tijani Reijnders put the visitors ahead in the 41st minute with a thunderous shot from well outside the penalty area.

But the Premier League outfit were more adventurous in the second half, equalising through a Said Benrahma penalty and then seeing Michail Antonio snatch a 76th minute winner.

“We have to be better, the analysis of the game is not that hard. We lost, so we didn't do well enough,” Jansen told reporters.

“In the first phase of the match they stormed at us, but after that we were in control and we scored a good goal. Our midfield held up well and showed very good things. Hopefully next week again,” the coach said about the return leg at the AZ Stadium next Thursday.

Goalscorer Reijnders said conceding after failing to clear corners had been sloppy on the part of his team.

"Two set pieces killed us, but with this result we can still look forward to the return in Alkmaar next week with great confidence. We showed what we can bring to the pitch. It is now up to us to keep that up for longer."