In a week that has seen their £58m striker offered around on loan and their brightest young star publicly courted by one of Europe’s biggest clubs, how Chelsea supporters must be thankful for Eden Hazard. The Belgium forward’s contract expires at the end of next season and he could yet find himself at Real Madrid one day, but he remains by far the most important player at Maurizio Sarri’s disposal as the Italian struggles to impose himself on English football.

It took a moment of brilliance to settle this as Hazard set up Willian – himself the subject of a rejected bid from Barcelona this week – to curl home from an acute angle and end Newcastle’s hopes of a point after they had equalised Pedro’s opener.

“Willian for us is really a very important player,” said Sarri. “We need wingers, so we need Pedro, we need [Callum Hudson-]Odoi, we need Willian, of course. For us, in this moment, he is a fundamental player.”

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Sarri said Chelsea lacked depth in key positions such as central midfield. “As you have seen, today Jorginho was in trouble and on the bench there wasn’t a player for that position, so I need a player, I need an option for Jorginho,” he said. “The club knows very well my opinion, I need the player there [but] it depends on the club decision.”

Watched by owner Mike Ashley as he continues to be frustrated in his attempts to sell the club, Rafael Benítez’s side battled hard but were undone by a lack of quality in the final third as they slipped into the bottom three.

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With Álvaro Morata injured and potentially on his way out on loan, Sarri turned to Hazard to lead the line as Hudson-Odoi made way for Pedro on the right flank. The 18-year-old – the subject of a £35m bid from Bayern Munich this week – has still to start a Premier League game and found himself on the substitute’s bench despite impressing in both cup competitions.

Unsurprisingly Benítez opted for a safety-first approach in front of his employer. Having stayed away for more than a year before he showed up at Selhurst Park in September for the 0-0 draw with Crystal Palace, Ashley attended six matches in succession but had not been seen since November, when news of a potential takeover led by former Chelsea chief executive Peter Kenyon first emerged.

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Even less surprisingly, he was greeted with a chorus of disapproval from the away end inside the first 60 seconds of the match. But, on his return to Stamford Bridge, Benítez got off to a terrible start when David Luiz’s brilliant long ball picked out Pedro’s run and he calmly lobbed the ball over Martin Dubravka. Yet Chelsea did not create another real chance until David Luiz headed wide in the 25th minute and they were pegged back just before the break. Ayoze Pérez had already served warning of Newcastle’s threat when he raced on to Salomón Rondón’s flick and poked his shot wide, but Ciaran Clark made no mistake with his header from Matt Ritchie’s corner.

“After the goal I think we thought, ‘now it’s easy’, but it wasn’t,” admitted Sarri. “We slept for 20, 25 minutes, so at the end of the first half we were in trouble. We need to improve in the mental reaction. After our first goal something happened. We need to improve.” Having touched the ball less than any other Chelsea player in the first period, Hazard dropped deeper in an attempt to spark his side into life and the result was almost immediate. His interchange with Willian saw N’Golo Kanté find space to set up Pedro for a shot, only for Dubravka to tip it wide of the post.

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Christian Atsu wasted a good chance for Newcastle in front but could not direct Ritchie’s cross goalwards. Pedro wasted another great chance from Marcos Alonso’s cross but after Newcastle failed to clear properly, Hazard pounced on the loose ball, wriggled past three markers and played in Willian to curl a sumptuous effort in off the far post.

It was Hazard’s 10th assist of the season, joining Lionel Messi as the only player from Europe’s top five leagues to have reached both that mark and 10 goals. Hudson-Odoi was serenaded with chants imploring him to stay when he came on for Pedro but Newcastle could have stolen the show had Rondón converted Javier Manquillo’s deep cross. “The reaction of the players after we conceded shows that they care,” said Benítez. “Hopefully everyone can see that the effort was were but it still was not enough. We have to stay calm because it’s a long-distance race. If we continue to play like we did today then we will have a good chance.”