Wolves went three-up thanks to Stephen Hunt's opener in the 20th minute and two goals from Sylvan Ebanks-Blake, the second a 37th-minute penalty after Blues goalkeeper Jack Butland was adjudged to have brought down Kevin Doyle.
But Clark's side hit back in the second half through two Wade Elliott goals- the first a 55th-minute penalty after Jamie O'Hara fouled Wes Thomas and the second in the 90th-minute when he fired home the rebound after his second penalty of the game had been saved by Dorus De Vries.
"Quite simply, without the ball in the first half we were rubbish, with it we were decent," Clark said.
"With it in the second half we were decent again and without it we were good. But in the first half we were woeful.
"Three or four players weren't at it and you can't have that. With the ball, you can have three or four players maybe not having a great day but without it, you have to have 11 putting a shift in.
"I think we got a little bit caught up and excited about what happened on Friday, thinking we could just turn up and play our football, forgetting you've got to win the battles.
"It's a very frustrating day for us when you think if we'd got three points we could have gone eighth in the table."