"I must admit, my heart was in my mouth at the time," admitted Johnson.
"The lads felt there was a bit of contact but from our point of view, maybe he was starting to go down early, we don't know.
"The referee was very brave with forty-odd thousand people screaming for a penalty, anyway.
Johnson also revealed that he had to make a late decision on who to play in goal as Adriano Basso had sustained a slight groin injury during the warm-up and so just five minutes before the side left the dressing room he had decided to play Dean Gerken.
"We made that decision at 2.55pm," the City boss added.
"Basso was grimacing a little bit and doing a stretch on his groin.
"I knew today we needed people to be 100% mentally and physically, and he didn't look either at the time.
"We were able to bring Dean Gerken in and on the day, I would have thought he was a candidate for man of the match."