Brown jumped in two-footed as he challenged with the Manchester City star, with Foden narrowly avoiding being seriously injured.
With the referee not making a decision on the foul, the challenge was referred to VAR to take a look. After being checked for serious foul play it was cleared.
Fans on social media were not so convinced, while Gary Neville also took issue with the tackle.
Taking to X, Neville said: "I said this a few weeks ago. When a player jumps in like that the fact the opposing players leg isn't broken doesn't alter the fact every professional hates that challenge more than any other.
"The intent can only be there to significantly harm your opponent."
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Luton made a brilliant start and found themselves 1-0 up thanks to Elijah Adebayo, before goals from Bernardo Silva and Jack Grealish earned a crucial win for Man City.
That victory ends a four-match winless run in the Premier League and puts Pep Guardiola's side four points behind league leaders Liverpool.