Arsene Wenger has said Alexis Sanchez's ankle injury is in a "terrible state" after the Chile forward was forced to come off during Arsenal's 3-1 loss at West Brom on Saturday.

Arsenal lost goalkeeper Petr Cech to a calf injury in the first half and Sanchez was then hurt in a tackle by James McClean shortly before half-time.

Sanchez, who had scored Arsenal's equaliser, played on after the break but was taken off in the 78th minute.

"He stayed on but in the second half he was not himself," Wenger told Sky Sports immediately after the game. "He just limped so I decided to take him off. And his ankle doesn't look good."

Later he added: "He was injured from the tackle in the first half. It was a bad tackle. His ankle is in an absolutely terrible state. He should not have played in the second half but he insisted that he wanted to come out.

"In the first half he was the one who created many chances, made dangerous situations and in the second half you could see that he couldn't anymore. In the end we had to take him off. He should not even have played in the second half."

Asked if he'll miss the upcoming Chile games, Wenger said: "Chile goes to Argentina for a massive game but they play only next week and if it's only a kick, he will play. If the ligament is damaged, he will not play."

Alexis Sanchez goes down in pain. Matthew Lewis/Getty Images

The news is a further blow to Arsenal, who have now lost four of their last five Premier League games and are in real danger of missing out of a top-four spot for the first time under Wenger.

They next face Manchester City after the international break, but will also be sweating on the fitness of Cech for that game. The goalkeeper pulled up after playing a pass out to the right side of his area and sat down shaking his head to indicate there was a serious problem.

He walked gingerly off the pitch and was replaced by David Ospina in the 38th minute, with the score tied at 1-1.

Minutes earlier, Cech had pulled off the best save of the game when he denied Darren Fletcher's hard shot with a one-handed stop.

It was Ospina's first Premier League appearance of the season, although the Colombia international has been the starter in Arsenal's Champions League and FA Cup campaigns. Cech also missed nearly a month last season with a calf injury.