All hope is not lost though for Robert Page’s side, who face England in the final game.
Gareth Southgate’s side are poised to advance, despite being held by the USA, and they currently lead Group B on four points.
Here are the permutations for Wales to advance to the last 16 and finish top:
What do England and Wales need to qualify from Group B?
England are not qualified from Group B yet after a goalless draw with the USA. Gareth Southgate’s side are on four points, with Iran, USA and Wales also still able to progress.
The equation is simple for the Three Lions: Avoid a four-goal defeat to Wales on Tuesday.
To secure top spot: Win. Simply. But top spot is still England’s if they draw unless Iran beat the USA or the USA beat Iran by at least four goals. Top spot is also England’s if Iran and the USA draw and they avoid a loss to Wales by four or more goals.
The route for Wales is trickier. The first part is arguably the hardest: Beat England and hope for a draw between the United States and Iran.
But if the USA vs Iran match is not a draw, Wales must beat England by four goals to advance.
To secure top spot: Beat England by four goals with a draw between USA and Iran.
The United States have a straightforward equation: Win. Iran have an easier route, a draw is enough, unless Wales beat England.
How is qualification decided?
Should teams be level on points after three games, then progress will be determined by goal difference, then goals scored, then the head-to-head results between the relevant sides. It then gets complicated from there...
Fair play: The team that advances will be the one who accumulates the fewest indiscipline points wins (this is totalled with one point for a yellow card, three points for a red card shown for two yellows and four points for a direct red card, plus five points for a player shown a direct red card while already on a yellow card).