Alonso set up Chelsea team-mate Olivier Giroud to score in the 3-2 win at Southampton
The Football Association is looking into Chelsea defender Marcos Alonso's tackle on Shane Long in his side's 3-2 win at Southampton on Saturday.
The Spaniard appeared to stand on the back of Long's calf in the first half as his team trailed 2-0.
If Alonso is charged with violent conduct then he faces a three-game ban and would miss Sunday's FA Cup semi-final against the same opponents.
He would also miss Premier League games at Burnley and Swansea.
The FA can take retrospective action if referee Mike Dean or any of the other officials failed to see the incident.
If that is the case, a three independent panellists then individually rule on whether Alonso's tackle warranted a red card and, if the decision is unanimous, an FA charge can be brought.
"It was a poor challenge - it should have been a red card in my view," said Southampton manager Mark Hughes after his relegation-threatened side's defeat.
"The disappointment was the officials didn't see it. They were all within a 10 to 15 metre radius - one of them should have seen it."