The 29-year-old Czech Republic international fell awkwardly at the end of a session and will now miss Saturday's Barclays Premier League clash with West Brom and the following weekend's visit of Norwich.
Blues boss Andre Villas-Boas said: 'Petr Cech suffered a medial ligament injury and will be out for three to four weeks.'
He added: 'It was the end of training, a normal training incident. He fell awkwardly with his weight on top of him. We expected much worse when we saw the incident.'
More to follow...
Injured: Petr Cech has been ruled out for three to four weeks with a knee problem
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Source: Daily Mail
Source: Daily Mail