It's claimed that Newcastle are believed to be one of the clubs interested in Armstrong, but Palace boss Roy Hodgson is an 'admirer' of the attacker from his work in the England setup.
Blackburn are seemingly aware of the interest, and would allegedly demand an eight-figure fee for Armstrong, with more than two years still left on his contract.
Paying eight figures for Armstrong would be tough to swallow for Newcastle, as Rafael Benitez sold him to Blackburn for just £3million less than two years ago.
Blackburn could more than triple their money on Armstrong if they do sell, and a return to St James' Park would surely be appealing to the 23-year-old.
Armstrong is a lifelong Newcastle fan, and spent 12 years coming up through the ranks with the Magpies, making 21 first-team appearances.
He was never really given a proper run though, and having gone away and thrived at Blackburn with 10 goals and six assists this season, he may feel he is in a better state to make an impact at Newcastle.
Capable of playing wide or up front, Armstrong could offer a versatile attacking option for Steve Bruce, and ease some of the goalscoring burden on the struggling Joelinton.
Still, paying more than £10million for a player sold for just £3million seems like something Mike Ashley wouldn't be too keen on, and the lingering threat of Palace is a concern too as interest mounts in the in-form attacker.
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