London - Liverpool roared back to form with a 5-0 demolition of Watford to stay one point clear of defending Premier League champions Manchester City, who squeezed past West Ham thanks to a Sergio Aguero penalty.

Behind the front two, the race for the remaining Champions League places is hotting up, with third-placed Tottenham just four points clear of Arsenal and Manchester United and Chelsea close behind.

Here are five things learned in the Premier League from the midweek fixtures:

Van Dijk turns scorer

Virgil van Dijk has been widely praised for his role in strengthening Liverpool's once-suspect defence, with the leaders having conceded just 15 goals in the Premier League so far this season.

But the Dutch centre-back also proved how useful he can be at the other end of the pitch, with two headed goals inside the closing stages of a thumping 5-0 win over Watford as Jurgen Klopp's men stayed a point clear of City.

Van Dijk, however, made no secret of his priorities after the match by saying: "It was great to score in front of the Kop and to keep a clean sheet was even more important".

City show resolve of champions

The sight of Manchester City taking the ball into the corner to run down the clock in the final stages to hold out for a 1-0 win was not what was expected from West Ham's visit to the Etihad.

However, just three days on from a draining 120 minutes to win the League Cup on penalties over Chelsea, Pep Guardiola's men did at least get the job done to keep the pressure on Liverpool.

City had to rely on Sergio Aguero's penalty and a big save by Ederson from Andy Carroll for the sort of three points that often make the difference in a tight title race.

Caballero repays Sarri faith after Kepa axe

Willy Caballero was left humiliated on the Wembley touchline when Kepa Arrizabalaga refused to give way to Chelsea's reserve goalkeeper during the League Cup final.

Manager Maurizio Sarri responded to the challenge to his authority by dropping Kepa for Wednesday's 2-0 win over Tottenham, and Caballero repaid his faith by producing a composed display in his first Premier League start this season.

It was a sweet moment for the 37-year-old, who said: "The very good news is that he doesn't care what happened. We are ready and Kepa was fantastic today in supporting me.

"He learns, we learn, and I thank him for supporting me."

Lukaku gives Solskjaer timely reminder

Marcus Rashford has blossomed under interim Manchester United boss Ole Gunnar Solskjaer, becoming the first-choice frontman and limiting opportunities for Romelu Lukaku.

But with Rashford on the substitutes' bench on Wednesday after a injury in the weekend draw with Liverpool, Lukaku stepped up to score twice in the 3-1 win at Crystal Palace -- his first goals in 10 games.

"He's had to play wide for me and had many defensive duties so I'm happy for him playing as a number nine," Solskjaer told the BBC.

"It's always good to see players taking their chance. That's what it's about at this club, when you get your chance, grab it."

Ozil seizes chance

Unai Emery has not been convinced by Mesut Ozil's contribution to Arsenal this season, but making just his second league start of 2019 the German showed what he can bring in a 5-1 mauling of Bournemouth.

Ozil got Arsenal off to the perfect start with a fourth-minute opener and also played a big role in the Gunners' second and third goals scored by Henrikh Mkhitaryan and Laurent Koscielny.

Given Emery's track record of dropping the club's highest earner for away games against top-six opposition, there is every chance Ozil will find himself on the bench again when Arsenal visit Spurs on Saturday.

However, Ozil has at least given Emery a tough decision to make.