Koscielny was carried off on a stretcher early in the first half after he fell to the pitch untouched and grabbed his right leg in pain.

Asked about the injury after the 1-0 loss, Wenger told BT Sport: "It's not good. It looks an Achilles rupture. Maybe we'll have good news, but the first signs are not good."

Wenger was a bit more cautious in his following news conference, saying that "you can always hope for a miracle in the scan that he will have but the first signs don't look very good."

But Wenger acknowledged that if the diagnosis is confirmed, the France international will miss this summer's World Cup

"If he has a ruptured Achilles, his chances [of playing at the World Cup] are nonexistent," Wenger said.

Koscielny has dealt with a number of Achilles injuries in the past and said a year ago he would need daily treatment for the rest of his career in order to to stay fit.

"Every morning I have my treatment for my Achilles and I know I need to do this to the end of my career," he said then. "Sometimes with all the games we play every three days, it is difficult and I need to have a rest to recover well."

Meanwhile, injured Arsenal teammate Santi Cazorla said Koscielny told him he had torn the tendon and will not make it to Russia.

"He told me it's his Achilles tendon," Cazorla told Cadena Ser radio. "He will miss the World Cup and be out of action for a long spell.

"It's a hard day all in all. It's a big loss because he is a very important player for Arsenal [and] for his national team and it's sad."

The 32-year-old started France's friendlies against Wales last November and at Russia in March and was set to be in a battle with Raphael Varane to start at centre-back alongside Samuel Umtiti.

Koscielny announced in November that he would retire from the France team after the World Cup.

Wenger called upon Calum Chambers to replace Koscielny in Madrid, but Arsenal could not find the goal they needed and crashed out 2-1 on aggregate.