Blues suffered their first defeat in 11 matches as Brighton & Hove Albion ran out 1-0 winners at the American Express Community Stadium.
David Lopez's 58th minute strike was the difference between the sides as the Seagulls moved into the play-offs with this victory.
Lee Clark made three changes from the New Year's Day draw with Barnsley
- Hayden Mullins, Mitch Hancox and Wade Elliott came in for Kyle Bartley, Dan Burn and Andy Shinnie.
Blues made a bright start and looked comfortable with the ball at their feet and nearly took the lead through makeshift centre-back Mullins whose
effort was cleared off the line by Keith Andrews.
As the half went on Brighton grew into the match more and more and dominated possession - but it took them until the 25th minute to test the excellent Darren Randolph
in the Blues goal.
Despite the hosts domination in possession, Blues limited them to long range efforts. Stephen Ward testing Randolph from the edge of the area as well as two long range efforts from Kazenga LuaLua in as many minutes just before the interval.
The Seagulls started the second half as they finished the first. Randolph had to be alert to smother the ball at the feet of Lua Lua who latched onto a poor pass from the Blues defence. Brighton kept pressing, good link up play between Leonardo Ulloa and Lua Lua opened up the Blues defence but the latter wasn't able to strike the ball as cleanly as he'd have liked and screwed his effort wide of Randolph's post.
On the 58th minute, Blues makeshift defence was beaten. Lopez fired the ball past Randolph from a tight angle after the Blues stopper had made a good save from Andrew Crofts effort.
After taking the lead the hosts carried on in the same vein to try and extend their lead. Randolph equal to Crofts' 25 yard strike only minutes after Lopez had opened the scoring.
Blues tried but couldn't force their way back into the match. Shane Ferguson's cross evaded Lee Novak and Nikola Zigic couldn't get enough on the ball to direct it goalwards.
Chris Burke had Blues best opportunities in the 90th minute, Paul Caddis played in Burke and from 15 yards out forced a good save from Tomasz Kuszczak. Then, 30 seconds later, from the resulting corner Burke fizzed a great ball across the six yard box but unfortunately there was nobody gambling to tap it in.
It could have got worse for Blues when Paul Robinson found himself with three Brighton forwards bearing down on him in the fifth minute of injury time but Randolph did well at the feet of Rohan Ince.
Despite Blues first defeat in 11 matches manager Lee Clark was pleased with the commitment his side showed and was pleased with his side's performance.