The Royals might have had a dream run in the Cup, but it hasn't gone to plan in the league as they are not yet safe from relegation going into the final two weeks of the season.
Reading's FA Cup exploits mean that they have only played 42 games this season, with the majority of the league having played two matches more and only two games from the season's end.
Steve Clarke's side are very unlikely to be dragged into the mire and they know that victory over the Blues on Wednesday will move them up to 18th and 10 clear of 22nd-placed Millwall, ensuring second-tier football for another season.
It meant that Reading couldn't go one better than their only other FA Cup last-four appearance in 1927.
No win also makes it six games without a victory in all competitions, while in the league they have won just two of their last 12 in what has been a wholly underwhelming season bar the FA Cup run for a team that was in the playoffs last term.
Clarke will be desperate for a win to avoid any relegation worry, but the Royals' record immediately after an FA Cup game this season has not been good with just one win out of five. They have also failed to score in five of their last seven games at home.
Recent Championship form: LLDDDL
Recent form (all competitions): LDDDLL
Like Reading, Birmingham have a different manager to the one that they started the season with. Gary Rowett's impact has been better than that of Clarke's and he is targeting a top-half finish with the Blues.
After just two defeats and an impressive eight wins in his first 12 games in charge, Rowett's side have shrunk back since mid-January with just four wins in 19 games.
Still, they are completely safe and if they can finish the season strongly a top-12 finish is a real possibility.
A haul of at least seven points from their remaining three games will probably be needed if they are to stand any chance of finishing in the top half, but two of their last three games are away from home, where they haven't won in the league since the turn of the year, losing five of their last six on the road.
A leaky defence has been their main issue of late, with no clean sheet in eight games and 14 goals conceded in that time.
On Saturday they only let one in, but that was only goal of the game as new league leaders Watford claimed the points at Vicarage Road. To be fair to Birmingham, little could be done about Craig Cathcart's impressive volley.
One of the most positive aspects of the Blues' season has been the rise to prominence of Demarai Gray, who scored a hat-trick when Birmingham last faced Reading. Keeping hold of the teenager will be a tough ask this summer, with Arsenal the latest club to be linked to the winger.
Recent form: LWLWDL
Clarke didn't make a substitution until the 90-minute mark against Arsenal, so could rotate and freshen up his lineup for the visit of Birmingham.
The Blues will be able to welcome back Watford loanee Diego Fabbrini, who was ineligible to face his parent club at Vicarage Road two days ago.
Reading possible starting lineup:
Federici; Gunter, Pearce, Hector, Obita, Williams, Ake, Karacan; McCleary, Pogrebnyak, Cox
Birmingham possible starting lineup:
Randolph; Caddis, Morrison, Kiernan, Grounds; Gleeson, Tesche; Cotterill, Fabbrini, Gray; Donaldson
Head To Head
Reading have won two of the last three meetings between the two, but were well and truly hammered 6-1 in the December reverse.
The Royals' record at home to Birmingham is decent, though, with four out of five victories when hosting the Blues of late.
The last goalless draw between the two sides was 16 meetings ago in 1996 when they were also both in the second tier.
We say: Reading 2-1 Birmingham
Reading might be a little more jaded following the demands of Saturday's game at Wembley, but they have more to play for and will want to put an end to their nasty winless streak. There should be goals, and we expect Reading to just edge it given Birmingham's woeful away form in 2015.