The Reds take a 2-0 lead to Old Trafford for the second leg of the last-16 clash after comprehensively outplaying their arch-rivals in their first meeting in European football.
Victory ended a run of four successive defeats to Louis van Gaal’s side and despite United putting up little fight against Liverpool’s total domination at Anfield, Henderson has sounded a cautionary note against complacency.
“It is only half the job done. Anything can happen in football and I have seen stranger things happen,” said the England midfielder.
“It is only half-time so we have to make sure in the second half at Old Trafford we play like that again because it will be very difficult.
“It was a good team performance. You have to concentrate on performances and I feel in the last few weeks performances have been good and results follow.
“We have built some momentum and confidence and hopefully we can continue that until the end of the season.
“This (result) give us another boost.”
Henderson admits he had to tread carefully after being booked in only the second minute for a raised foot which is routinely cautioned in European football.
The players had been warned by manager Jurgen Klopp before the match to be careful as Spanish referee Carlos Velasco Carballo had a reputation for being card-happy, having issued 74 cautions and six red cards in his 12 previous matches.
Carballo took his tally to 80 bookings with three apiece for each side, the most significant of those for the hosts being the one shown to Dejan Lovren who together with Alberto Moreno (both on two) will be suspended for the quarter-finals should they collect another yellow card and Liverpool progress next week.
“I was a little bit concerned getting a yellow card after two minutes,” admits Henderson.
“I didn’t think it was a booking but maybe a foul as my studs were showing but I got the ball.
“I just needed to be careful and not make any silly fouls as I could easily have been sent off but I felt I managed myself well.”
Klopp said he did think some of the official’s decisions were harsh but did not want to complain about his performance, although it did concern him of the impact going forward.
“We didn’t know how to handle it. It was really hard for Hendo after his early yellow card,” he said.
“We don’t have to criticise the referee because he didn’t decide the game but for the whole tournament it is difficult.
“There are a few yellow cards on each side and you think ‘Why?’ “The team that goes through will have a problem with yellow cards.”
Klopp was careful not to get too carried away with the performance and goalkeeper Simon Mignolet was equally wary ahead of next week’s short trip to Manchester.
“We are pleased with the result and not to concede at home in a two-legged game,” said the Belgium international.
“We could have scored more but it is still undecided and we have to stay calm and look forward to the next game at Old Trafford.
“But (because) we’ve done it (in the first leg) it doesn’t mean we’ll go through to the next round.
“Manchester United at Old Trafford is always going to be a tough fixture; they have loads of individual quality throughout the squad and we have to deal with that.
“But we have to look at our performances and we have the talent. If we play the way we did then we don’t have to worry about that.
“We’ve got a whole week to focus on the game. It’s not happened very often this season with the amount of games we’ve played so that’s positive.
“We can recover and focus on the game but I am sure Manchester United players are fit enough to play two games in a week.
“We’ve got an advantage and we’re happy with the way we played, but we have to do it again next week.”