Darron Gibson's season could be over after he ruptured an anterior cruciate ligament that requires surgery with the Everton midfielder facing a lay-off of up to nine months.
Gibson suffered the injury while playing for the Republic of Ireland in a World Cup 2014 qualifier on Tuesday evening. However, given that the structure of the 25-year-old's knee is not damaged there is confidence at Everton that he will make a complete recovery.
Gibson, watched by his club manager Roberto Martínez, collapsed during the first half of the 3-1 over Kazakhstan at the Aviva Stadium, requiring several minutes of on-field treatment before being stretchered off.
After a scan on Wednesday revealed the extent of the damage, Everton released a statement that said: "Darron Gibson is set to undergo surgery on his injured knee. Gibson was stretchered off during the first half of the Republic of Ireland's 3-1 win over Kazakhstan on Tuesday evening. A subsequent scan showed he has damaged his anterior cruciate ligament (ACL) and the midfielder will require an operation.
"The length of time the 25-year-old will be best determined once the surgery is completed. However, the scans did confirm to Everton's medical team that no additional damage was sustained to the structure of the right knee, ensuring all treatment and rehabilitation will be focused on repairing the damaged ACL."
The injury comes as a blow to Gibson after he missed the start of the season with a previous knee injury and to Martínez, whose side have lost only once in the league to stand four points behind the leaders, Arsenal, who have 16.
The Spaniard hailed the Everton players who helped their respective nations qualify for the 2014 World Cup finals on Tuesday evening. Of the USA's Tim Howard, Costa Rica's Bryan Oviedo and Belgium's Kevin Mirallas and Romelu Lukaku, Martínez told evertontv: "Once you have a player involved in the international scene, you want them to be successful. You want them to enjoy their experiences and nothing gets bigger than being able to perform in a World Cup.
"That's something we are going to follow closely in the summer but now it's a matter of getting everyone back fully fit and concentrating on working towards our aims which is very important. The name of Everton is going to be taken to Brazil and many other countries and that's very important. But now it's about thinking day to day and making sure the players are enjoying their football, growing and maturing."