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Leeds were a minute plus stoppage time away from booking their place in the fifth-round draw after a superb goal from Felix Nmecha, but Patrick Roberts's long-range strike deflected in off James Justin to force extra time.

Roberts went from hero to villain in the shoot-out, firing wildly over the crossbar after Lucas Perri had repelled Tommy Doyle's kick, as Leeds avoided an upset.

Leeds only attempted three shots – one of which was on target – through the first half, with Birmingham almost taking a surprise lead in the 11th minute. Jay Stansfield rifled off a left-footed volley from near the corner of the area, but Perri expertly tipped it onto the woodwork.

Perri also got down well to prevent Demarai Gray's drive from nestling in the bottom-left corner, but after making it to half-time and introducing club captain Ethan Ampadu, Leeds began to force the issue.

They went ahead when Noah Okafor fed Nmecha in the left-hand channel, with the striker firing beyond Ryan Allsop with no backlift after cutting inside his marker in the 49th minute.

Birmingham, which felt Nmecha may have strayed offside in the build-up, saw Ibrahim Osman slip when presented with a good chance to level, but they got their goal when Roberts' 89th-minute drive flicked off Justin's head and whistled into the top-left corner. 

Osman side-footed against the post and Kanya Fujimoto was unable to make the rebound count in the seventh minute of second-half stoppage time, then Dominic Calvert-Lewin and Ampadu went close for Leeds during extra time.

Neither team could find a goal to avert a shoot-out, and after four perfect kicks, Doyle and Roberts – two of Birmingham's star performers – fluffed their lines, allowing Sean Longstaff to score Leeds' winner.