The 24-year-old was tipped to be part of Gareth Southgate's 23-man squad for the tournament in Russia after an impressive season with Swansea, despite their relegation, but he will have to wait it out as he heals for the upcoming season.
The player's knee problem is believed to have stemmed from an injury he suffered in a warm-up ahead of an FA Cup match at Sheffield Wednesday last February. But he still managed to emerge as one of the Swans' best performers in what was an underwhelming overall campaign.
The player, seemingly intent on starting next season fully fit, opted to have his knee surgery at the end of the term. But the Welsh side will struggle to hold on to him, given he attention he has attracted from Premier League sides.
Mawson joined the Swans for just £5m on a four-year deal from Barnsley in 2016, and he's likely to make them a neat profit if sold this summer.