Everton and Wales defender picked up a nightmare injury during his national team's friendly against Mexico on Tuesday, suffering a collapsed lung after colliding with West Ham United striker Javier Hernández.
The 33-year-old centre-back uploaded pictures of his injuries, via the Mirror, and stated that he would be flying back to the UK following treatment in hospital, with the aim of recovering in time for the start of next season's Premier League campaign.
Williams suffered a number of breaks to two ribs, which punctured his left lung and led to the collapse.
The veteran defender came under fire repeatedly for his substandard performances for Everton last season, a far cry from his dogged displays in Euro 2016, where Wales defied the odds to reach the semi finals. Williams will hope for an improved campaign next season, as his side look to recover from an underwhelming 2017/18 Premier League showing.
The former Stockport County man spent much of his career with Swansea City, playing a key role in the side's promotion from the Championship in 2011, and becoming a reliable Premier League centre back as his side established stability in the English top flight. Williams has 79 caps for Wales, and scored in their stunning 3-1 win over Belgium in Euro 2016.
Meanwhile, Everton are still in the dark over whether they will be successful in their pursuit of West Ham United forward Marko Arnautović this summer, after the Austrian reacted coyly to claims he could leave the Hammers.
The 29-year-old is also believed to be being targeted by Man Utd, but the Toffees are likely to push hard to secure the tenacious forward's services.