Cardiff stretched their lead to seven points at the top of the npower Championship with a 1-0 win at Birmingham.
Joe Mason's 41st-minute strike made the difference at St Andrew's, with the former Plymouth striker turning the ball in after an error from home goalkeeper Jack Butland.
Hull stayed second following a goalless draw at Blackpool, after Middlesbrough stumbled to a 3-1 loss at Derby. Michael Jacobs, Jeff Hendrick and Conor Sammon put Derby 3-0 ahead, with well-beaten Middlesbrough mustering a 90th-minute reply from Lukas Jutkiewicz.
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