Coutinho—on loan at Bayern Munich from Barcelona—was a major success in his five-year spell on Merseyside. He joined the Reds in January 2013 for a reported £8.5 million and left for the Camp Nou in January 2018 for an initial sum of £105 million.
Few might have expected UEFA Champions League titleholders Liverpool to thrive quite so successfully since then, and Henderson told Sport (h/t Goal's Chris Burton) he doubts his former team-mate will be back:
"Phil is a good friend of mine. I think he is an exceptional footballer, he has everything, he has a great attitude and he loves football. So, of course, for me he would always be welcome, but it is not up to me.
"It is probably best to ask the manager that. The boys loved him, so if you ask any of them, I'm sure they'll say they would love to have him back.
"But I think his time here has passed; he has moved, and I hope that in the near future we will see the same Phil we saw here."
Liverpool made it to their first Champions League final in 11 years the same season Coutinho was sold, winning their sixth European crown one year later when they beat Tottenham Hotspur 2-0 in Madrid, Spain.
Henderson and Co. bring a 14-match unbeaten run into their round-of-16 clash with Atletico Madrid, whom they face at the Wanda Metropolitano—the site of last season's triumphant final—on Tuesday.
Atletico manager Diego Simeone lauded Liverpool for their ability to improve despite selling Coutinho, who was largely viewed as their best player at the time, per the Liverpool Echo's Paul Gorst:
Coutinho hasn't been so successful since he parted ways with Jurgen Klopp's side, who boast a 25-point cushion at the top of the Premier League.
The 27-year-old scored 11 goals and recorded five assists in 54 total appearances for the Blaugrana over the course of the 2018-19 campaign before he was sent to the Allianz Arena on temporary terms.
Henderson is one of numerous players who has elevated his performances under Klopp's command, while investment in players like Virgil van Dijk, Alisson Becker, Fabinho and Andrew Robertson has proved shrewd.
The Athletic's Red Agenda podcast recently discussed the slim chance of a Coutinho comeback on Merseyside:
Bayern signed the winger on a season-long loan for €8.5 million (£7.8 million), per the Press Association (via Guardian), but it seems unlikely they'll pay the £109.8 million required to turn the deal permanent.
The official Bundesliga YouTube account highlighted Coutinho's direct goal contributions up to mid-January, including a haul of three goals and two assists during a 6-1 drubbing of Werder Bremen in December:
It doesn't seem plausible that Liverpool would be willing to pay the kind of sum Barca will likely want for Coutinho should he move again this summer, and his contract in Catalonia doesn't expire until 2023.
The South American made 201 appearances for Liverpool and was a firm fan favourite before any talk of a Barcelona transfer emerged, but both Henderson and the Reds appear to have moved on.