Alex Davey will remain with Peterborough United until the New Year.
The 20-year-old defender initially joined the Posh from Chelsea on a one-month deal in early August but will now remain at London Road until January 2.
Davey has impressed in League One so far this season, making seven appearances, and winning the Man of the Match award against Gillingham on the weekend.
Chelsea's official website read: "Alex Davey has extended his loan at Peterborough until 2 January."