The Bees almost pulled off a remarkable upset, but Fernando Torres saved the Blues' blushes by equalising late in the game to force a replay at Stamford Bridge.
Chelsea's away form has been imperious under Rafael Benitez, winning four successive trips away from SW6, but Reading will be tricky opposition, especially when you consider that the Royals have put together a run of four consecutive victories.
Brian McDermott's side are just a point away from jumping out of the relegation zone, while the Blues have a four-point cushion on fourth-place Spurs and will be keen to close the six-point gap between themselves and Manchester City who are second.
Reading will likely be without long term casualties Jason Roberts (hip) and Alex McCarthy (shoulder).
Nicky Shorey and Hal Robson-Kanu both made successful returns from injury against Sheffield United in The FA Cup last weekend.
The only other concern for the Royals would be the new Portuguese signing Daniel Carrico, the former Sporting Lisbon player is struggling to build up match fitness since his January move to the Premier League.
Chelsea continue to miss the Nigerian duo of Jon Obi Mikel and Victor Moses, a loss that is understated by most, with the Super Eagles continuing their bid to win the African Cup of Nations.
Eden Hazard will continue his suspension for the red card that he received against Swansea in the League Cup last week. Reading will be the second game that the Belgian will miss of an initial three-match ban, but the FA continue to examine evidence as to whether he merits a harsher punishment for the "ball boy incident."
John Terry completed the 90 minutes against Brentford and appears to have fully recovered from his MCL sprain, although David Luiz continues to struggle somewhat with a calf problem. Oriol Romeu remains the only other absentee, long-term, through injury.
Projected Blues team
Petr Cech; Cesar Azpilicueta, John Terry, Branislav Ivanovic, Ashley Cole; Frank Lampard, Ramires; Juan Mata, Oscar, Marko Marin; Fernando Torres.
The main dilemma for Benitez will be whether to include Terry from the start after coming through the game against Brentford on Sunday or whether to use precaution given that it has only been a couple of days since his return on the field.
Ivanovic was left out against Southampton in the last match that Benitez used David Luiz as a centre-back, which suggests to me that it could be Cahill's turn to be rotated out of the starting lineup should Terry start consecutive games.
There are hardly any alternatives for Benitez in the midfield as David Luiz continues to struggle with injury, so I fully expect Lampard and Ramires to continue their partnership.
Torres should remain the man to lead the Chelsea attack, especially after notching a fine goal at the weekend. The Spaniard will certainly be joined by Oscar and Juan Mata, but the third tenor remains open to question.
Marin appears to be a better fit than Bertrand, who fails to offer a cutting edge in attack. The German winger can at least glide past his opposite number as well as link through the middle.