Goals from Naby Keita and Roberto Firmino earned Liverpool a 2-0 win over Porto on Tuesday as Jurgen Klopp's side took the upper hand in their Champions League quarterfinal tie despite not killing off their Portuguese opponents.
There remains plenty of work to do for the Premier League leaders, who will be disappointed they were unable to gain a bigger advantage for next week's second leg.
On a bitterly cold night at Anfield, Liverpool were well below their best and Porto deserved credit for a determined performance after going two goals down in the opening 26 minutes.
The visitors fired an early warning shot with Moussa Marega blasting narrowly wide in the second minute but the home side took the lead three minutes later through a Keita shot which deflected off Porto midfielder Oliver Torres and beat the helpless Iker Casillas.
Mohamed Salah then forced Casillas into a low save with a sharp shot on the turn, but the Egypt international should have done better in the 22nd minute when he placed the ball wide when through on goal, after picking off a sloppy Porto pass.
The Brazilian should have added to his tally, but blasted over after a good cross from Henderson.
The dangerous Marega then had a low drive well saved by the legs of Liverpool keeper Alisson as Porto showed they were not about to roll over.
Porto shouts for handball on Alexander-Arnold were waved off after video review following Alisson's saves from Marega.
Sadio Mane had an effort ruled out for offside three minutes after the interval, but apart from another Marega effort in the 69th minute there were few clear-cut chances in the second half.
The Portuguese side fought well to stay in the game in a scrappy second half to give themselves a chance of a comeback at home in next week's second leg on April 17.
Information from Reuters was used in this story.