Dario Vidosic admitted Arsenal punished his team's mistakes as they went down 5-0 at the Emirates to suffer only their second defeat of the season in the WSL.
Arsenal were 3-0 up after 24 minutes before adding two second-half goals. Albion went closest when Kiko Seike hit the bar in the second half.
Vidosic said, "It was a tough night. We know they are a fantastic team, and we came here to try and make it as difficult as possible but we got it a little bit wrong in the first half. We had a plan but couldn’t put it together and when that happens top teams will punish you.
"In the second half there were moments when what we wanted to do was there, but then sometimes sloppiness happened, we switched off in moments and they have very good players who can hurt you.
"It was a night to learn from, especially how to keep these good teams down for longer. Defensively we got caught a few times and we have to learn quickly if we are going to challenge the top sides.
"We wanted to be brave and test ourselves against the best, but it didn’t quite happen. There are still a lot of positives so we will pick ourselves up and prepare for next week."
Albion lost Maria Thorisdottir (calf) and Aisha Masaka (shoulder) in the second half.
"Maria got a bump on her calf and Aisha’s shoulder might have dislocated. We are a bit thin on numbers so we’ll try to keep everyone else healthy," added the head coach.