It was, in some respects, a trademark entrance from the Liverpool midfielder. Wataru Endo had been introduced barely three-and-a-half minutes earlier when he unceremoniously upended Lucas Paqueta for a free-kick to West Ham United.

But that Endo was on the pitch in the first place underlined both the manner in which the Reds were destroying the Londoners on Sunday and the fact the Japan international is going to be required during the next month.

Endo would be the first to admit his second season at Liverpool has been in stark contrast to his debut campaign when, after a slow start acclimatising to his new environment, the 31-year-old became a key player as the Reds challenged on four fronts.

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This time around it says much that Endo's 33-minute run-out from the bench during the 5-0 triumph at the London Stadium - Arne Slot's side 4-0 ahead when he was introduced - was his longest appearance in the Premier League this season. He had previously made just seven substitute outings, with only one seeing him introduced earlier than the 87th minute.

Endo has also seen only a couple of minutes of action in the Champions League, although he has started all three victories in the League Cup.

Of course, it was at the start of last year that Endo, having established himself in the first team under Jurgen Klopp, was absent for five weeks as he skippered Japan to the Asia Cup quarter-finals. Now, though, January could be an important month for Endo to step out of the shadows and assume an important role as Liverpool prepare for a hectic schedule.

Endo has had a long wait. It quickly became apparent during pre-season that Slot saw Liverpool's midfield moving in a different direction, with Curtis Jones, Dominik Szoboszlai and, finally, Ryan Gravenberch utilised in a double pivot along with Alexis Mac Allister, whereas Endo largely operated as the sole defensive midfielder the previous campaign.

Liverpool, though, rejected a bid of almost £12million from Marseille for Endo with a number of other clubs having also shown interest in the player. And while playing time has been at a premium - barely 300 minutes in the Reds' 27 games so far this campaign - Endo's outings have gradually impressed.

“I sometimes, at certain clubs or other teams, see a player coming in a bit like ‘you only use me for five or seven minutes?’," explained Slot after one cameo from Endo towards the end of the 1-0 win at Crystal Palace in October. “But if you look at how Wata came in now, how good he was on the ball but also the second balls that he won, he had only in these seven minutes a very good impact."

Slot was similarly enthused with Endo's performance at centre-back in the 2-1 League Cup quarter-final triumph at Southampton before Christmas.

“If I have to give someone a big compliment it should be Wata Endo, because in a different position, playing such a good game in these circumstances, that shows you what a quality player he is but maybe mainly what kind of mentality and personality he has," said the Reds head coach.

“He was one of the main players why we could win this game and he deserves all the respect from me, from his team-mates and also from the fans.”

While in some respects assuming the role James Milner acquired during the latter stages of his Liverpool stay of using his experience to help see out games, Endo's ability to play centre-back - a position in which has featured more than any other during his career - could prove crucial over the next month.

With Joe Gomez expected to be sidelined for an extended period with a hamstring problem and Ibrahima Konate still closing on a return after almost six weeks out with a knee issue, Jarell Quansah and skipper Virgil van Dijk are at present the only fit recognised senior centre-backs available for Liverpool.

Having been a regular starter in the League Cup, Endo would be primed to line up in the semi-final first leg at Tottenham Hotspur next Wednesday, and will be expected to start in the FA Cup third round tie at home to League Two strugglers Accrington Stanley three days later.

The final two Champions League games - at home to Lille on January 21 and at PSV Eindhoven eight days later - would also seem likely for involvement, particularly the latter should it end up a dead rubber. And, in early February, the return home leg against Tottenham would offer another opportunity for Endo.

His extended outing at West Ham, then, ensured much-needed minutes under the belt ahead of what is likely to be a busier next month or so for Endo. The chances of the Japan international leaving during the January window appear slim. Slot needs Endo more than ever.