The Czech Republic goalkeeper made a desperate last attempt to help his side snatch a point from their game against the Premier League strugglers but was seen struggling to return to his goal after the set piece was cleared upfield.
Cech has subsequently been ruled out of Saturday's north London derby against Tottenham but insisted he did not harm himself when making the late surge towards the opposition goal.
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"For a lot of people it looks more interesting to say that I got injured running back from the corner but the reality is I had already injured a calf during the game in the last 10 minutes," he told BT Sport.
"Obviously running to the corner I knew I probably wouldn't be able to run back [due to the injury] - or at least not fast. But it was the last minute and I thought we at least have the chance to get a point and it's not necessary that you go and score - you can create confusion, there is an odd number [of players], anything can happen, so this why I went.
"Obviously the corner came too far to the back post and the counter attack was coming. The referee was communicating over the radio and I could still hear he was saying there was like five, 10 seconds remaining and they will probably have a chance to score.
"I started running back although I knew that I probably can't. But I kind of tried, but you can see I was not running fast at all and obviously I reached a point in that run where I could not run any more and stopped. But I had already done [the injury] before [the corner] and so I knew I wouldn't be able to run back.
"It was kind of a bitter end of the game for me because we wanted to get three points to close the gap and in the end we lost and I got injured as well."