Saturday 27 January
Kick-off: 1500 GMT
Referee: Phil Dowd (Staffordshire)
Replay date (if required) : Tues, 13 Feb, 2000 GMT
Coverage on the BBC Sport website and BBC Radio Five Live
Birmingham midfielder Stephen Clemence is back after injury and defender Radhi Jaidi returns from suspension.
On-loan Arsenal striker Nicklas Bendtner, Mikael Forssell and Rowan Vine are all out.
Reading striker Shane Long faces a late fitness test on a thigh problem but left-back Nicky Shorey has recovered from food poisoning.
Dave Kitson, Kevin Doyle, Ibrahima Sonko and Brynjar Gunnarsson (hamstring) are all out.
Reading (from): Federici, Hahnemann, Murty, Bikey, Sodje, Ingimarsson, De la Cruz, Shorey, Seol, Sidwell, Harper, Oster, Convey, Hunt, Little, Lita, Long, Osano, Cox.
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BIRMINGHAM CITY pulled off one of the shock scorelines in the third round when holding Premiership Newcastle United to a 2-2 draw at home, and then thrashing them 1-5 at St James' Park, in the live televised replay. That's landed them this home tie with another top division side, and pits two managers who've both won the competition with Manchester United. Birmingham's Steve Bruce lifted the Cup in 1990 and 1994 - Reading's Steve Coppell was a winner in 1977.
Bruce's side have not played a League game since losing at Ipswich on New Years Day. Their last two fixtures have been postponed, which has also seen them lose top spot in the Championship table. They're 14 places lower than Reading.
Last season's quarter-finalists, who were embarrassed to the tune of 0-7 by eventual winners Liverpool at St Andrews, have not lost in seven home matches in all competitions since Liverpool dismissed them 0-1 in the fourth round of this season's Carling Cup on 8 November.
READING are looking to avenge defeat to Birmingham in the fourth round of the FA Cup last season. Twelve months ago the Royals drew 1-1 at the Madejski, with a second half goal from David Dunn cancelling out Shane Long's first half opener for the home side. The Brummies won 2-1 with a goal in each half from Mikael Forssell and Julian Gary - either side of a Steve Hunt effort for the Royals.
Steve Coppell's side have been the surprise package in their first ever season of top flight football. They're undefeated in four League and Cup matches in 2007, including the rearranged third round tie against Championship Burnley. They won 3-2 at the Madejski, after the original game was postponed due to a waterlogged pitch.
The 1927 semi-finalists are trying to reach the last 16 for only the second time in 72 years. They were last in round five in 1998, when they lost to fellow Division One Sheffield United. They've not been knocked out by lower League opposition for five years, since Division Three York City won a second round clash at Bootham Crescent in December 2001.