David Dunn saved Birmingham from an FA Cup exit at Reading after the Championship leaders had threatened to add the Premiership side to their long list of conquests.
Dunn was one of a trio of changes made by disgruntled Blues boss Steve Bruce just before the hour mark and the former Blackburn man was instrumental in breathing life into a previously listless performance.
Reading had appeared to be on course for their ninth straight home win after Tipperary teenager Shane Long had fired them ahead.
But Dunn provided an equaliser and the top-flight side went on to finish the stronger.
Steve Coppelll rested a host of regulars to give John Halls, the new £250,000 signing from Stoke, an instant debut at right-back and Graham Stack, Stephen Hunt, John Oster, Chris Makin, Leroy Lita and Long starts.
Bruce was without the suspended Matthew Upson and injured duo Kenny Cunningham and Martin Taylor so had to rejig a back four featuring his 21-year-old son Alex and the rarely-used Olivier Tebily.
Reading began with a flurry of corners but the first real chance of the afternoon fell to the away side, with Muzzy Izzet heading over from 10 yards after Chris Sutton had flustered the normally reliable Ibrahima Sonko into a poor clearing header.
That had followed a mysterious off-the-ball incident involving Jermaine Pennant, which had seen Hunt hit the turf but referee Rob Styles did not launch too lengthy an investigation.
The Blues' make-shift back line had looked comfortable enough until it was found wanting in the 32nd minute.
James Harper, who was winning the midfield battle with skipper for the day Steve Sidwell, produced a fine angled throughball to take Tebily out of the equation and put Long into a shooting position on the right of the box.
The young Irishman had made little impact until then, with Lita, the hat-trick hero against West Brom in the previous round, even more anonymous. But Long showed exactly why Coppell had thought him worthy of a start with a low drive of precision and conviction to beat Maik Taylor in the Birmingham goal.
Reading were still looking comfortable and Bruce senior made his displeasure known in the 58th minute with a triple substitution. Emile Heskey, Jiri Jarosik and Izzet were the men hauled off to be replaced by Mikael Forssell, Dunn and Neil Kilkenny.
Within seconds Dunn had fired a passable chance over the bar but was back to force goalkeeper Stack, deputising for rested first-choice Marcus Hahnemann, into his first real save of the afternoon. His diving header from Pennant's invitation was made from some way out however and the former Arsenal man was able to get behind it.
But Dunn had already sparked life into Birmingham and was on hand to net the equaliser in the 67th minute. Again Sutton was involved, heading on a long throw into the box by Mario Melchiot and when no defender could intercept Dunn gleefully despatched it at the back post.
Birmingham now looked the side more likely to supply a late winner, although Tebily was booked for a foul on Long in the 75th minute and Melchiot was hurt defending the free-kick that followed.
The Dutchman recovered and almost supplied a winner with 10 minutes remaining after Dunn had again stolen in at the back post to set up a chance. Melchiot met it with his head from inside the six-yard box but Stack had come to meet him and made a point-black parry.
John Oster was booked following a clash with Pennant and the thoroughly-rattled Sonko followed him a minute later for a rash hacking down of Forssell 20 yards in front of goal.
Pennant's free-kick was well hit but Stack dived to his right to keep it out and Sutton's claims he had been impeded by Oster as he chased the rebound went unheeded.
