The Royals lost 2-0 to Watford last time out and have now dropped out of the playoffs, while Cardiff are seven points worse off after going three games without a win.
Reading had a four-point margin on the chasing pack just a month ago, but a run of one win in six has seen them drop down the table into seventh place.
Friday's disappointing defeat at Vicarage Road opened the door for Barnsley and Bournemouth to pounce, and both sides have taken full advantage of Reading's recent blip.
That is not to say the Royals' promotion hopes are dead and buried, though, as they still have six games to make up a five-point gap on either Barnsley or Bournemouth.
With those two sides not in action until later in the weekend, Veljko Paunovic's men have a chance to increase the pressure with victory against Cardiff on Friday.
While the Royals' form has been inconsistent over the past month, they have won three and drawn one of their last four at home.
Reading also have a very good record against Cardiff, going 10 without defeat in this fixture since November 2015, though six of those matches have finished all square.
Cardiff's own promotion hopes were effectively ended this week after being pegged back late on in a 2-2 draw with Blackburn Rovers.
That loss, combined with victory for Bournemouth in their midweek game in hand, means that Mick McCarthy's side are 12 points off the playoffs with 15 points to play for.
City have gone three games without a win since beating rivals Swansea City 1-0 nearly a month ago, having also lost to Nottingham Forest and Sheffield Wednesday since then.
Indeed, the Welsh side have conceded eight goals and scored twice across those three fixtures, which McCarthy will be looking to put right in Berkshire on Friday.
However, the Yorkshireman has lost his last six away league matches against Reading since a 2-0 win for Sunderland in March 2004.
John Swift is in contention for a return to the Reading side after missing their last 14 matches through injury, though that is likely to come from the substitutes' bench.
Cardiff's disappointing run has coincided with the absence of skipper Sean Morrison, who is not expected to return against his former side on Friday.
Kieffer Moore has enjoyed a fine first campaign for the Bluebirds but is clearly in need of a rest, though McCarthy does not really have any alternative options up top.
Reading possible starting lineup:
Cabral; Yiadom, Holmes, Moore, Gibson; Rinomhota, Laurent; Meite, Olise, Ejaria; Puscas
Cardiff City possible starting lineup:
Smithies; Nelson, Flint, Brown; Sang, Vaulks, Ralls, Ng; Wilson; Murphy, Moore
We say: Reading 2-1 Cardiff City
Reading have more to play for than Cardiff heading into Friday's match, with their playoff hopes still alive heading into the final straight.
The Royals have a good record at the Madejski Stadium and are without defeat against Cardiff in 10 games, so we are backing the home team to edge this one.