The Portland Timbers were awaiting test results on Darlington Nagbe's left ankle following a scary injury Sunday night against the Los Angeles Galaxy.
Nagbe, who also has been playing for the U.S. national team, had to be taken from the field by stretcher after he was tackled roughly by Galaxy midfielder Nigel de Jong.
Referee Allen Chapman gave de Jong a yellow card for the challenge, but Major League Soccer's disciplinary committee could issue a suspension.
Nagbe, 25, left the match in a wheelchair.
Timbers coach Caleb Porter expressed concern after the game that de Jong was not shown a red card. If de Jong is suspended, it would mark the third straight week that Portland has seen an opposing player suspended after the fact.
"If we're going to have an initiative to send a message on tough tackles, let's starting doing it for every game, not just some games," he said. "Tough part is we should have been up a man which could have impacted the result. Instead we end up getting a top player hurt and now another Western Conference team gets the benefit next game, not us."
De Jong apologized to Nagbe following the tackle.
"It was a pity; it was never my intention to hurt him. He's a good kid, as well, and I said that after the game, as well, to him. It's a pity, but that's football, as well," he told reporters. "It was never my intention, and when a ball comes in that situation, you always go for it 100 percent. Unfortunately, I caught him."
De Jong, who is from Amsterdam and plays on the Netherlands national team, broke a leg of American midfielder Stuart Holden during a March 2010 exhibition, kicked Spain's Xavi Alonso in the chest during the 2010 World Cup final and broke a leg of Newcastle's Hatem Ben Arfa that October.
The Timbers and the Galaxy played to a 1-1 draw.