Rangers manager Steven Gerrard insists Alfredo Morelos was chosen as penalty taker before today's game after El Bufalo fluffed his lines from the spot.
The striker had the chance to grab an equaliser in the 1-0 defeat to Celtic , but his shot was saved by Fraser Forster.
The Gers dominated the play but lost to Christopher Jullien's second half goal.
Gerrard told BT Sport: "I can't really ask any more from my players in terms of the performance and what they tried to do today. I thought we were really good.
"But we got one big moment wrong. We never defended the set piece.
"There's a good possibility two or three of them are offside (for the goal) but we've still got to defend it better.
"Over the 90 minutes we were superior. It always seemed as if the action was where we wanted it to be, but that doesn't win you big football matches."
Rangers were playing against 10 men for almost half an hour after Jeremie Frimpong was sent off for bringing down Morelos .
James Tavernier has missed from the spot three times this season and El Bufalo stepped up, but the Colombian saw his kick saved by Fraser Forster.
"Alfredo was the nominated penalty taker. It was certainly a big moment for him from a personal point of view.
"In terms of what was going through his mind, you'd have to ask Alfredo."
Morelos is yet to score a goal against Celtic, and club legend Ally McCoist feels he needs to step up his efforts.
Speaking after the match he said: "If you want to be a top-class Rangers striker you need to score against Celtic."
