Liverpool continue to pass every Premier League test that comes before them.

For the 18th time in a row, the Reds were victorious in their top-tier game on Monday.

This time, it was West Ham who were on the losing end, but the Hammers put up a good fight. They even led 2-1 going into the last half an hour, but goals from Mohamed Salah and Sadio Mane gave Jurgen Klopp's men all three points to restore their 22-point lead at the top of the table.

Here, we take a look at three things the soon-to-be champions learned against the London outfit.

Henderson is vital

In their previous match, the Reds succumbed 1-0 to Atletico Madrid in the Champions League. The defeat in itself was a blow to the current European champions, but Jordan Henderson's hamstring injury made matters even worse.

The aftermath of that clash saw Liverpool's captain ruled out for three weeks, with the game against the Hammers being the first time he has been absent from the starting line-up since the 5-2 victory against Everton in December. Coincidentally, that was the last occasion the Reds conceded two in the top flight.

Without him, they lost some of the defensive stability that has seen them concede just 17 times all season. Whilst he may not be the most technically gifted player in the squad, his presence and voice on the field are qualities that are vital to Klopp's team. He has been tipped to win PFA Player of the Year, and his bid to win that personal accolade was done no harm despite him not featuring.

In two weeks time, Liverpool will try to overturn that deficit to Los Rojiblancos in Europe, and it will be touch and go whether £31.5m-valued Henderson - as per Transfermarkt - will be fit to play.

If he is unavailable, he would be a huge loss to the Reds.

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Alexander-Arnold is Liverpool's most important player

Trent Alexander-Arnold and Andrew Robertson have revolutionised the full-back position over the past two years, and they were both at their best against the Hammers on Monday. The latter got himself an assist by laying on Mohamed Salah's equaliser, whilst the former went one better and provided for for Georginio Wijnaldum's and Sadio Mane's strike.

The 21-year-old now has 12 Premier League assists to his name this term - as many as he managed in the whole of the previous campaign - with his tally for the season in all competitions now at 14. His creative input can not be underestimated - he has created at least 29 more chances than any of his teammates this time out, and is the third-youngest player since 1992 to register 25 assists in England's top tier after Wayne Rooney and Cesc Fabregas.

Week after week, Alexander-Arnold is illustrating that he may just be Liverpool's most important player.

It is vital that Klopp's keeps him wrapped up in cotton wool as he goes in search of a historic treble.

Oxlade-Chamberlain provides impetus, Keita in trouble

In Henderson's place, Naby Keita was given the nod in central midfield. Whilst he didn't embarrass himself - he made two key passes and four tackles - he clearly didn't do enough to impress his boss, and he was hooked off with 57 minutes on the clock.

He was replaced by England international Alex Oxlade-Chamberlain, who gave the Reds the extra impetus they needed to turned around their one-goal deficit. The former Arsenal man has been an important squad player this season, scoring seven goals in all competitions.

For Naby Keita, though, this is another blow to his future at Anfield. The Guinea international has struggled to make his mark on Merseyside due to injuries and poor form.

Klopp's decision to withdraw him is unlikely to be good for his confidence, and time may well be running out for him to impress ahead of the summer window.