Chelsea will today hope to discover the extent of the ankle injury which could rule captain John Terry out of the hectic festive schedule. The England skipper left Emirates Stadium on crutches, his right foot in a protective cast, after the 1-0 defeat at the hands of Premier League leaders Arsenal, which ended the Blues 16-match unbeaten run. Chelsea manager Avram Grant is already without leading striker Didier Drogba, who recently had knee surgery and is set to join up with the Ivory Coast for the African Nations Cup after his rehabilitation. However, the Israeli coach hopes the prognosis on Terry - caught by a late lunge from Arsenal midfielder Emmanuel Eboue at the end of the first half - will not be too severe. 'He is not feeling well, but he didn't break anything. There is possible damage to his ligament, but we will wait for Monday to see how it is,' said the Chelsea boss, whose casualty list also includes Ricardo Carvalho, Michael Essien. On the positive front, long-term absentee Michael Ballack could be considered for Wednesday's Carling Cup tie against Liverpool. However, Grant admitted he was looking at bringing in reinforcements in the January transfer window. 'If we didn't have injuries and the African Cup coming up the squad is good enough,' he said. 'We are checking everything. We want to bring in players that are good for the quality of the team but it is not easy.' Arsenal's victory keeps them one point ahead of Manchester United, six ahead of Chelsea and 10 in front of Liverpool, who languish in fifth place. It was a first defeat in 17 matches under Grant, and the crucial goal came when former Blues defender William Gallas headed in a corner during first-half stoppage time following a rare mistake by Petr Cech. Grant said: 'Petr Cech is a great goalkeeper with a great attitude - but it happens even to the big ones. I'm disappointed it happened in this game. 'It is disappointing but if we continue like this it is not the end of the world. 'Six points at this time of the season is nothing. It will not be easy, but it is not something that we could not do something about.' Grant believed referee Alan Wiley was correct to show nine yellow cards - and did not complain over the treatment handed out to Ashley Cole, who was booed at every turn on his first return to Arsenal since his controversial transfer to Stamford Bridge. Full-back Cole was reported to have made a gesture to the Arsenal fans as he left the Emirates pitch following an altercation with Cesc Fabregas in stoppage time. 'They made a lot of fouls on him, but he is a big boy and it is not a problem,' said Grant. 'He played well and it gave him more motivation.'