Liverpool had won each of their previous four home leagues games in which they conceded first and 12 minutes later they had turned another match on its head as Roberto Firmino's trickery set up Mane to give the hosts the lead at the second attempt.
Images from the Europa League matches played on Thursday
De Boer, who lasted only 77 days as Crystal Palace manager after losing his first four league games in charge with no goals scored, said in an interview on BT Sport that it was "a pity" Mourinho was Rashford's manager because he was not getting enough chances.
News of all that's transpired on and off the football field
Dejan Lovern talks about his ambition to become a Liverpool legend at Anfield and why victory in the Merseyside derby against Everton could propel Reds' chances this season.
Barcelona battled back from a goal down and scored twice in the second half to overcome hosts Borussia Moenchengladbach 2-1 in their Champions League Group C match on Wednesday despite the absence of the injured Lionel Messi.
Cristiano Ronaldo renewed his personal battle with Lionel Messi by scoring his 71st Champions League goal, putting him three behind the Argentine's newly-set record, in Real Madrid's 1-0 win at FC Basel on Wednesday.