Argentina, led by the legendary Lionel Messi, faces a critical match with Poland as it attempts to qualify for the knockout rounds Wednesday.

Group C is tightly packed with Poland standing at 4 points, Argentina at 3 points and underdog Saudi Arabia at 3 points. Mexico is at the bottom of the table with 1 point, but it does have a chance of making the next round.

If Poland or Argentina wins outright, it will qualify for the next round. If Saudi Arabia defeats Mexico, it will also improbably make it to the knockout stages. But who advances otherwise gets more complicated from there.

Mexico needs to defeat Saudi Arabia if it wants to advance, but they still would need to get a helpful result in the Poland-Argentina match (either a Poland win or a draw and advantageous goal differential). A draw in both matches would put Argentina and Saudi Arabia tied at 4 points and come down to goal differential as well. Poland would win the group.

Group D is more clear. France has already qualified for the next round, so they may take it easy against Tunisia. Tunisia would need to beat France, get a draw in Australia-Denmark and win out on goal differential.

The Aussies would advance with a win against Denmark. Denmark can only advance with a win, though it would need a better goal differential than Tunisia if the African country upsets France.

Here is Wednesday's schedule:

U.S. star Christian Pulisic was taken to the hospital for scans on his abdomen after the team's win over Iran.

Pulisic sustained an injury after he slammed into Iranian goalkeeper Alireza Beiranvand while scoring the eventual game-winning goal late in the first half. Though he stayed down for several minutes and had to be helped to the sideline, he did return to the game.

The 24-year-old was substituted out at halftime. U.S. head coach Gregg Berhalter said immediately following the game he did not have an update on Pulisic's condition. The U.S.'s next game is Saturday.

President Joe Biden celebrated the U.S. win over Iran at the World Cup following remarks in Bay City, Michigan. He walked back up on stage and delivered his congratulations:

“USA! USA! That’s a big game, man. Well, I spoke to the coach and the players and said, ‘You can do it,'” Biden said.

He continued, “They did it. God love ‘em! Anyway, just thought you might want to hear.”

The U.S. will face the Netherlands at 10 a.m. on Saturday in the knockout round.

-ABC News' Ben Gittleson

The United States has advanced to the knockout stage of the World Cup with a 1-0 win over Iran.

Walker Zimmerman played hero for the U.S. in the 98th minute when he cleared a loose ball from just feet in front of their net.

The U.S. finished second in Group B and will face the Netherlands, the winner of Group A, in the knockout round.

Belgium entered the World Cup with the No. 2 ranking in the world with its so-called "Golden Generation" looking at one last chance to win the tournament. Now, the team is fighting just to advance to the knockout stage.

All eyes will be on Romalu Lukaku, the star forward for Belgium who has been recovering from a hamstring injury, to see if he can play and play well. He came on as a substitute in the squad's second game for his first action of the tournament. He'll start Thursday's game on the bench too, but figures to be an important substitute.

Belgium, currently third in Group F, faces Croatia, which stands atop the group. A win for Croatia puts them in the second round and officially eliminates Belgium. A win for Belgium would also put them through. A draw and it gets more complicated, with Morocco also in contention.

Morocco is facing off with Canada, which is unfortunately already eliminated from advancing to the knockout stage in its first World Cup appearance since 1986. At 0-2, the country would still like to get its first World Cup victory ever. Morocco would clinch a spot in the second round with a win. If both matches end in a draw, then Croatia and Morocco would go through to the knockout stage.

The second slate of games Thursday features longtime soccer power Germany fighting to stay alive. The country sits last in Group E with just 1 point. They'll need to beat heavy underdog Costa Rica just to have a chance to advance. If Germany wins and Spain beats Japan, Germany would get through.

Spain or Japan would advance with a win as they play each other. Spain would also advance with a draw, but Japan would only advance with a draw if Germany loses or ties or Germany wins and Japan has the better goal differential.

Here's the schedule for Thursday: