Clarke hailed his side's spirit after a clattering encounter in which the visitors hit the woodwork twice through Pavel Pogrebnyak and Oliver Norwood, and which captain Alex Pearce finished with a broken nose.
But he denied they would be considered hot favourites to progress to the semi-finals for the first time since 1927 when the Royals face the Bantams for the second time on their controversial replay date.
Clarke said: "When the draw was made I said it was a 50-50 tie and I believe it is still a 50-50 tie as both teams showed today that they are quite evenly matched.
"It was a good old-fashioned Cup tie between two fully committed teams. It was a physical game with no quarter asked and no quarter given and both teams just looking for that lucky bounce of the ball."
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