Alexander Isak has informed Newcastle he wants to explore his options this transfer window.

There has not been an official or formal transfer request to date. There have been conversations about a new contract at Newcastle in the last few months. However at this stage nothing has been agreed.

Isak has three years left on his deal so Newcastle are in a strong position in terms of transfer value, and value him at £150m. They insist he’s not for sale.

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Look at our picks of the best goals from Alexander Isak’s Premier League career so far with Newcastle

The Swedish striker was sent home by Newcastle manager Eddie Howe ahead of the 4-0 pre-season defeat to Celtic last weekend due to being affected by transfer speculation following an approach from Liverpool.

Isak then wasn’t part of the travelling party to Singapore today, with Newcastle saying he was left at home due to a minor thigh issue and a long-haul flight wouldn’t have helped his recovery.

But the speculation is a contributing factor to Isak being left behind in Newcastle.

Liverpool made an informal approach for Isak last week before signing Hugo Ekitike – and it’s believed they remain huge admirers of Isak.

What did Newcastle boss Howe say about Isak last week?

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Eddie Howe said on Saturday that he’s ‘confident’ Isak will stay at Newcastle

Newcastle boss Eddie Howe speaking after Alexander Isak was sent home from the squad ahead of the 4-0 defeat to Celtic last Saturday:

“It was my decision. He travelled to Glasgow with us but I decided to send him home due to the speculation around him.

“The last thing he wanted is to be sat in the stands watching, that wasn’t fair to him. But I’m confident he will be a Newcastle player come the end of the window.

“We have a few of those players who are irreplaceable. Your top players are so hard to find, so hard to recruit and so hard to develop.

“So when you have them, you need to treasure them. Of course we’re desperate to keep him as part of our team.

“I’ve had discussions with him, but that’s not abnormal. I respect a player’s career and how short it is. Alex has been really good, he’s trained really well and I realise there’ll be noise around him.”

Could Wissa replace Isak at Newcastle?

Meanwhile, further talks are happening on Thursday at Brentford over the future of Yoane Wissa amid Newcastle‘s interest.

The player wants to go but Brentford do not want to sell him after they sold Bryan Mbeumo to Manchester United for £71m.

Brentford’s valuation of Wissa has increased after Mbeumo’s sale because it is seen as a risk to lose both players.

The pair scored 39 goals between them in the Premier League last season.

Sky Sports News has been told Brentford value Wissa at no less than £40m.

Newcastle, who have been increasingly hopeful they can get him for around £35m, do not want to overpay for a player they currently see as a number two striker to Isak.

Analysis: What do Newcastle do now?

Sky Sports News’ Keith Downie:

“Newcastle wanted to use this window to build, they wanted to bring in four players. A goalkeeper, a central defender, a right winger and another forward.

“They’ve brought in Anthony Elanga, they wanted a second striker to come in and compete with Alexander Isak. They had those talks with Frankfurt [about Hugo Ekitike], Liverpool hijacked that and still retain an interest in Isak as well.

“It’s not what the Newcastle fans want to hear ahead of a Champions League season where they’ll be battling on two major fronts. They want to hold onto their best players – the last thing they want to hear is Isak’s head being turned.

“Eddie Howe is a great man manager but he’s going to have to do the best man management job of all time to try to get Isak into a positive frame of mind going into the season.

“Reading between the lines, the fact he’s asked to explore his options, his head has been turned. He’s been left back here in Newcastle, one due to the injury but also because he’s been affected by the interest.

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Speaking before Isak’s desire to leave, Newcastle signing Anthony Elanga says he can’t wait to join up with his Sweden teammate at Newcastle and hails him as one of the best strikers in the world

“Isak is one of the best players in the Premier League, he’s arguably the best striker in the Premier League. He feels he should be paid similar to the top strikers, and he’s not at Newcastle. If he moved to a new club, whether that’s Liverpool or elsewhere, he would be remunerated in that way.

“The club are going to have to come to some kind of conclusion here – does he get a pay rise? Do they let him speak to other clubs? Or do they allow time and space for the situation to calm down over the next few weeks?

“But you ask me what happens now, either someone comes in and stumps up the £150m Newcastle are looking for, or Isak signs a new contract or bigger money, or he just gets his head back into being a Newcastle player – and begins the season in a positive frame of mind.

“But it’s a delicate situation, this one. The last thing Eddie Howe wanted, the last thing Newcastle fans wanted. Howe sounded exhausted after the Celtic game on Saturday. There’s no sporting director at the moment, they’re looking for a new CEO too.

“Eddie Howe and his nephew Andy have been involved at the front of the whole transfer plan this summer, and Newcastle have been bruised. They’ve tried for Liam Delap, Joao Pedro, Dean Huijsen and been unable to get any of them.

“Newcastle are still in advanced negotiations over a deal for Yoane Wissa, but he was meant to be the back-up to Isak, not their only striker.”

Sky Sports to show 215 live Premier League games from next season

From next season, Sky Sports’ Premier League coverage will increase from 128 matches to at least 215 games exclusively live.

And 80 per cent of all televised Premier League games next season are on Sky Sports.