Steve Long fired the home side into a first half lead at the Madejski Stadium but substitute David Dunn's second half goal earned Blues a replay at St Andrew's in ten days time.
Black, standing in for manager Steve Bruce, who was unable to speak after the match because of a sore throat, said: "It was always going to be a very hard match. Reading are top of their division, they are full of confidence and energy so it was always going to be difficult.
"To be 1-0 down at half-time obviously made it even harder but our second half response was superb and probably we could have won the game in the end.
"I thought it was a scrappy affair first half and although they scored the goal they didn't have that many clear-cut attempts at goal and we certainly didn't.
"But the response in the second half is what we have to look at and hang on to because we have come away and got a good result at a very difficult ground."