Darren Moore admitted his side lacked any cutting edge after his first official game in charge ended in defeat.
The Baggies were disappointing and were punished by a disciplined Bolton Wanderers side who snatched all three points with a last minute winner.
Albion had more than 70% of possesion and 20 shots on goals but failed to create any real clear-cut chances.
It took a fantasic individual effort from new loan signing Harvey Barnes to drag the Baggies level but were toothless for long spells in the Championship opener.
"We huffed and puffed, got into some good areas of the pitch but probably could have been more effective," Moore admitted.
"We came up against a disciplined, resolute rearguard. We know how difficult that style is to play against because we've adapted that over many seasons in the Premier League and got results against very good teams.
"It's a difficult system to break down. But it shows that when teams come up to The Hawthorns we've got to find ways of breaking them down.
"We had plenty of possession and I was happy with that. We need to work a little bit more on having that cutting edge in the final third.