It really funny reading that United is interested in signing Jackson. I just hope this is not true because of all the strikers in the world, they couldn't see any to sign but "Chelsea's reject"? 
If they cannot sign a better striker because of limited funds or lack of european football, they should just stick with the ones they've got or go for Ollie Watkins instead.
Manchester United is truly serious about bringing in a player who has actually played in the Premier League. Therefore, their options likely aren't far from Premier League clubs. So, I'm not surprised that Jackson is their target. Moreover, Manchester United likely sees this opportunity as uncertain, as Chelsea have other players who appear to be better. Therefore, Chelsea wouldn't mind letting Jackson go.If they cannot sign a better striker because of limited funds or lack of european football, they should just stick with the ones they've got or go for Ollie Watkins instead.
Even Nicolas Jackson isn't just sought after by Manchester United. La Liga giants Barcelona are also interested in this young striker.1 Besides his relatively young age, he's also quite a prolific goalscorer. So, I personally don't find what Manchester United are doing particularly funny. However, Manchester United fans maybe will certainly expect more from Jackson if Manchester United are truly serious about improving their attack.
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Reference:
1. https://disway.id/read/885471/mengejutkan-barcelona-bakal-pinjam-stiker-chelsea-nicolas-jackson-50-juta-euro