The England forward has missed a number of spot-kicks over the years, but he was coolness personified as he sent Jose Sa the wrong way to score his 100th Premier League goal on 67 minutes following Joao Coutinho’s handball.
"Our best taker by far is Riyad,” said the boss.
"He has shown under pressure he can do it. Gundogan is another but he wasn't on the pitch because he has pain in his back and he has struggled in the last few games with it and with the position, so we have to reflect what we have to do to recover him.
“So, in that moment they choose. Bernardo is a good taker, Rodri could do it, but Raheem wanted to and he scored the goal - I appreciate this.
“The guys who miss still take responsibility to do it.”
Asked about Sterling’s confidence, Pep added: “Players are always important, but they sometimes drop.
“They have highs and lows. I am unfair sometimes; they play well and I don't play them.
“I don’t have an excuse, he scored goals lately and is so committed and aggressive and he has been incredibly important over the years.
“But players have to perform every single game. He is really good, aggressive, and attacks, and this is important.”