Birmingham were condemned to defeat by two Danny Guthrie set pieces either side of half time, but Clark believes that his players matched Reading for most of the game.
"In terms of the football in terms of the territory I think we more than matched Reading," Clark told the club reporter.
"The difference was we weren't clinical in the final third. Our composure and our decision making could have been better in the final third.
"But we certainly created lots of situations and we passed the ball around. When the second goal went in we were in the ascendency. We've been undone by two bits of quality."
The defeat leaves Birmingham in 19th place having won just one of their last seven Championship matches.