The striker, who arrived from Southampton in June, is yet to score for his new club and spurned his best opportunity yet when his first-half spot-kick saved by Christian Abbiati.
|10/1||Rickie Lambert is 10/1 with William Hill to be Liverpool's top scorer|
"I spoke to Rickie and I said to him it's only important when it matters in the competition phase," Rodgers told the club's official website.
"He is obviously disappointed because he can't remember the last time he missed a penalty because he never missed one for Southampton. He will be fine. Rickie will get goals for us, there's no doubt."
Rodgers was pleased with his side's overall display and hailed the "maturity" of the performance at the Bank of America Stadium.
"As we gain our fitness throughout the games I think it's clear you see the tactical development being introduced into the team," the Northern Irishman added.
"Our possession of the ball was very good, we kept the ball and kept it moving, and then when we had to defend I thought we were really aggressive in our pressure and intensity. We had maturity in our game."
Liverpool take on United - 3-1 winners over Real Madrid - on Monday.