Arsenal striker Alexandre Lacazette says they must be wary defensively at Valencia next week.

Lacazette struck twice as they won the first-leg of their Europa League semifinal 3-1.

"We conceded the first goal and we knew they were good on set pieces. At this moment we concede too many goal on set pieces. We need to be careful on this for second leg," Lacazette told BT Sport.

"We have a lot of quality in this group and we can go to the final. We know the next game will be difficult but if we have the same ingredients there then we will go through,' he added.

"It's our target to reach the final and win this trophy. We know it's an opportunity to qualify for next year's Champions League."