The Merseyside club created many goalscoring opportunities at the Hawthorns in a match where they also saw Daniel Agger sent off with the score at 1-0.
"The feeling after was one of total shock with the result. It was never a 3-0 game," said Gerrard.
"I fancied us to go there, dominate and win but things didn't work out that way. In football you can be left feeling hard done by.
"It's not the start we wanted but it's no time for panic. It's only the first game and it was one bad day at the office. We've got to look at the bigger picture. There's been so much hope around the place and rightly so."
Liverpool's next game in the Premier League is against Manchester City on Sunday.