The knee injury that Henderson sustained at Borussia Dortmund last week could potentially end the captain’s season, which despite his unconvincing form, was a blow to manager Jurgen Klopp.
The 25-year-old had been dovetailing nicely alongside Emre Can, on the whole, and he was part of a Reds side improving by the week.
While Henderson’s underrated industry will be a loss to Liverpool between now and the end of the season, it has suddenly given three midfielders a real chance to prove their worth.
With Can now the undisputed first choice in the middle of the park, Milner, Allen and Stewart will all feel they can feature prominently next to him between now and the end of 2015/16.
The trio all outlined their differing qualities in Sunday’s 4-1 win over Stoke at Anfield, performing impressively throughout.
Ever since arriving on a free transfer from Man City last summer, Milner has split opinion among the Liverpool fanbase.
His gritty, unsung style of play means that was always going to be the case, and in truth, his performances for the Reds have not always convinced.
There have been good days at the office, when his positive attributes have been there for all to see, but there have also been days when he has been running in treacle, looking completely off the pace both on and off the ball.
The 30-year-old has enjoyed a very impressive last couple of outings for the Reds, though, and there are signs that he is going to finish the season strongly.
The England international was one of the standout players in what was an excellent draw in Dortmund, with his all-action style and intelligence coming to the fore in a central midfield role.
Against Stoke, Milner was a strong contender for Man of the Match, standing in as captain in Henderson’s absence.
Everything he did was bordering on faultless, from his off-ball work to his use of the ball in possession, and he thrived in both a three-man midfield and a diamond.
Milner has proven big-game experience, and with the massive second leg with Dortmund on the horizon, he is someone Klopp can rely on.
The 30-year-old is not the long-term solution, but for the foreseeable future he should be an invaluable squad player.
There isn’t a Liverpool player who has both improved more significantly and become more popular than Allen this season.
The Welshman was ridiculed so much during his first couple of years on Merseyside, with Brendan Rodgers’ embarrassing dad-like behaviour towards him certainly not helping.
Under Klopp, he has morphed into the class act that Rodgers always waxed lyrically about, and has been one of the Reds’ best players in 2016.
Every time he has been called upon he has delivered a seven-out-of-10 performance at worst, and it has now reached the stage where selling him would be a huge error.
Allen was immense against Stoke on Sunday. His pressing was relentless, he looked silky with the ball at his feet and there was just an overall swagger that was never evident between 2013 and 2015.
Maybe that Andrea Pirlo-esque look has made all the difference.
Allen has actually been very unfortunate not to feature more in recent months, with his form far better than Henderson’s has been.
He did a better job than the skipper when he replaced him at half-time in Dortmund, and will surely start against Thomas Tuchel’s side in the return leg.
It was great to see the 26-year-old receive a deserved standing ovation as he left the pitch on Sunday, and he has won over the doubters at a fairly remarkable rate.
It may be that Allen wants to move on this summer, in order to play more football, but he is a very good footballer who Klopp must try and keep hold of.
Having shone during the early part of the year, Stewart has almost become a forgotten man following a two-month lay-off with an ankle injury.
He was handed his first ever Premier League start against Stoke, and although it may not have been the most testing of matches, he passed with flying colours.
The 22-year-old has a certain class and confidence in possession that you cannot teach – someone like Jay Spearing never had it, for example – and he was a figure of real authority at the base of the Liverpool midfield.
He played two key passes during the game – only Milner made more – and he was a physical brute, winning a sizeable 64 percent of his duels.
Stewart is understandably less likely to feature as much as Milner and Allen in the coming weeks, but he is now a player who can be relied upon.
The midfielder has come from nowhere this season, and has now leapfrogged the likes of Jordan Rossiter, Cameron Brannagan and Pedro Chirivella in the pecking order.
This summer is sure to be a huge one for Liverpool, with Klopp set to make significant changes to his squad, but Stewart has shown that he will pick players on merit.
His future is certainly up in the air, given the competition in his area of the pitch, but he may have several chances to prove his worth before the season is done and dusted.
It would be going overboard to say that the Englishman is a future Reds regular, but he has been bright and influential every time he has featured in 2015/16.
The trio of Milner, Allen and Stewart all showed exactly what they can bring to the table against Stoke, and are all good options for Klopp in the absence of Henderson.
There is a definite argument to say that all three should be retained by the German ahead of next season, and their performances in the coming weeks could prove key to that decision.
Milner’s vast experience and hugely underrated quality have been particularly on show in the last few matches, and he offers more positives than negatives.
Allen, meanwhile, has been a revelation during Klopp’s tenure, with the former Swansea City man one of Liverpool’s most in-form players.
He is excelling in all areas of his game, and assuming he is selected against Dortmund, he will be a key figure against a side of real class.
A new contract must be offered in the summer.
Meanwhile, with Klopp having handed Stewart a new long-term contract back in February, the German is clearly a fan of the midfielder.
He always allowed youngsters to prove themselves during his Dortmund days, and should Stewart get a regular starting berth between now and May, he may be keen to keep hold of him.
Henderson’s injury was not ideal by any means – regardless of what many of his detractors will tell you – but it has allowed others to stamp their mark on the team.
Milner, Allen and Stewart were all stand-out players against Stoke, and they will feel they can play a big part in what is hopefully a trophy-winning end to the campaign for Liverpool.