Gordon was handed his 20th successive top-flight start for the contest at Stamford Bridge, but the winger limped off in the 35th minute after sustaining a knee injury following a collision with Marc Cucurella.
Either side of Gordon's withdrawal, Alexander Isak netted a superb equaliser on the stroke of half time to cancel out an early opener from Nicolas Jackson, but the Blues regained their advantage courtesy of second-half goals from Cole Palmer and Mykhaylo Mudryk.
Gordon's replacement Jacob Murphy scored a 90th-minute thunderbolt to give the Magpies hope of a late comeback, but they were eventually condemned to their 12th Premier League defeat of the campaign – seven more than they lost in the entirety of last season – and remain 10th in the table, three points behind the top seven.
Commenting on Gordon's condition after the match, Howe told reporters: «He is in a bit of pain and we fear it is not looking too good but it is very early days.
»That was a huge moment in the game to lose him then. He has been so good for us this season and so consistent. That is another psychological blow for the players."
Howe added: «I think [Gordon's knee pain] was quite early on in the game, but as I said, there was no moment where he felt an injury, just the pain was there. So we sent someone over because he didn't look like he was moving right. And then eventually he succumbed to the injury.»
Gordon has been a standout performer for Newcastle in his first full season at the club, contributing with 10 goals and seven assists in 39 appearances across all competitions.
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