Lukas Jutkiewicz's second-half equaliser earned Birmingham a deserved replay as their fourth-round FA Cup tie at Huddersfield ended 1-1.
Jutkiewicz arrowed home a low shot nine minutes into the second period after Steve Mounie's emphatic header had given the Premier League side an interval lead.
Another bite at the cherry was just reward for Steve Cotterill's Sky Bet Championship strugglers, who comfortably held their own against Huddersfield, who still look out of sorts after their recent top-flight struggles.
Terriers head coach David Wagner made wholesale changes again after his side's third-round win at Bolton - seven in all - and Blues counterpart Cotterill made the same number.
Both sides have important league games on Tuesday, with Liverpool visiting the John Smith's Stadium and Birmingham playing Championship relegation rivals Sunderland.
Birmingham looked more comfortable with all their changes in the early stages and Jutkiewicz fired the wrong side of a post in the 16th minute from Carl Jenkinson's right-wing cross.
Blues' £6million-plus midfielder Jota, making his first start since Boxing Day, as usual caught the eye, but Huddersfield took the lead through their first moment of Premier League quality, which ended in Mounie's fifth goal of the season.
Florent Hadergjonaj swept the ball into the box from the right after exchanging passes with Collin Quaner and the Benin international's thumping downward header gave Birmingham goalkeeper David Stockdale no chance.
Quaner's angled shot was tipped over by Stockdale soon after and Mounie headed over the crossbar as Birmingham's threat waned before the break.
Philip Billing made his second appearance off the bench following his 14-month ankle injury lay-off sooner than expected in place of Danny Williams, who had taken a knock.
Jonathan Grounds replaced Brentford defender Harlee Dean during the interval and the second half unfolded in the same uneventful vein as the first.
But Jutkiewicz lifted Birmingham's 2,500-strong travelling fans in the 54th minute, latching on to Michael Hefele's botched clearance and drilling a low 20-yard shot via a slight deflection into the bottom corner.
Stockdale saved well from Billing's thumping shot and Mounie blasted off target as Huddersfield responded, while Jota slipped the attention of several defenders to fire narrowly wide.
Jutkiewicz's header was ruled out for offside as Blues served another warning and at the other end Abdelhamid Sabiri's effort flashed inches wide.
Former Middlesbrough, Coventry and Burnley striker Jutkiewicz threatened again for Blues after rolling his marker just inside the box, but Joel Coleman rescued his jittery defence with another smart save.
Terriers' substitute Scott Malone's mis-kick two yards from his own goalline in the closing stages summed up his side's afternoon, while in stoppage time another substitute, Joe Lolley, blazed a golden chance over the crossbar following Quaner's cutback.