The Liverpool manager conceded he has a major task to restore confidence after César Delgado's stoppage-time winner consigned the Anfield club to a fourth successive defeat for the first time in 22 years. He is likely to be without Gerrard for the Premier League match with United, with the captain aggravating an adductor strain for the third time this season, while Fernando Torres, Glen Johnson and Albert Riera are all doubts for Sunday, when a fifth straight defeat would leave Liverpool 10 points behind Sir Alex Ferguson's side.
The loss to Lyon left Liverpool, twice Champions League finalists under Benítez, languishing third in Group E and likely to need to win their three remaining group games to reach the knockout phase, a feat they achieved two seasons ago. It also intensified the spotlight on the club's manager, who says he retains the appetite to resurrect Liverpool's miserable campaign.
"It is very disappointing. It was a difficult game for us but we were winning and had two or three chances to change everything," said the Spaniard. "Then we conceded in the last minute. We had too many problems before the game and it is really disappointing.
"It was a difficult game but we could have won and now we have to lift ourselves for Sunday. It is something we have to do. We have to prepare the players, push them and keep going. Now it is a question of doing things properly and to have the confidence that we can do it [against United]. Had we taken our chances tonight everything could have been different.
"For me it is simple, I have to prepare for the next game. That is my job and I will do that as soon as I finish this press conference. We have to be ready for our next game. For me personally, my staff and the players will be there, everyone who wants to see Liverpool winning."
Liverpool travel to Lyon in a fortnight where defeat, coupled with another Fiorentina victory over the bottom club Debrecen, could leave Benítez's team with a mountainous task to escape Group E. "I think we need to win all our matches now," said the Liverpool manager. "We have done it before and we have to do the same again. We have to have the confidence that we can do it again."
Benítez's team were floored by Delgado's winner, his fellow Lyon substitute Maxime Gonalons having equalised Yossi Benayoun's first-half opener, and events on the night conspired against Liverpool. Johnson was ruled out before kick-off with a tight groin and his replacement, the impressive 19-year-old Martin Kelly, was injured attempting to prevent Gonalons' leveller. But it was the loss of Gerrard that could have lasting repercussions.
The Liverpool captain missed Saturday's league defeat with an adductor problem collected on England duty and is likely to miss the United game after suffering a reaction last night. But Benítez said: "It wasn't a risk to play Stevie. He wanted to play and the doctor said he was OK. He has trained for the last two days but sometimes it is bad luck. I think it is the same problem as before and we will check him and the other players tomorrow."
Benítez was left in no doubt that supporters' patience is wearing thin. The manager's decision to replace Benayoun with Andriy Voronin in the 85th minute prompted a chorus of disapproval around Anfield but the manager was unrepentant.
"The fans know Yossi is a quality player but I thought he was looking a bit tired and I wanted to use fresh legs and quality," he said.