Assistant boss Henk Ten Cate revealed Didier Drogba was due to take the crunch fifth spot-kick in the shootout.
And that forced Terry to step into the breach - and with the score at 4-4, the Blues skipper had the chance to win the Champions League.
But the England defender slipped on his run-up, scuffed his shot and hit the outside of the post.
Ten Cate said: "John was not in the first five to take a kick but things change during a game.
"Some people feel sick and the sending off of Drogba made us change it.
"It's unbelievable this should happen to him though.
"We practised penalties so much all last week and he was very confident. We were all very confident."