On the back of scoring his first goal in a Reds shirt [vs. Southampton on Friday], the summer signing was handed his third start in the competition against the Portuguese visitors.
And only five minutes into the encounter, he opened the scoring for Jurgen Klopp's men, benefiting from a deflection after being set up by Roberto Firmino.
Later in the first half, the Brazil striker doubled the Reds’ lead after Mohamed Salah missing a good chance earlier.
Just after the restart, Sadio Mane thought he had put the hosts 3-0 up only to be adjudged offside. Moussa Marega was a constant threat for Liverpool's backline, but the Porto striker could not convert his chances as the Reds held on for a victory.
Tuesday’s game was Keita's fifth Champions League appearance for Liverpool who visit Portugal in a fortnight for the reverse fixture as they look seal progression into the semis.