Carlo Ancelotti believes Yury Zhirkov will play a crucial part in Chelsea's Barclays Premier League title defense.Zhirkov was recently warned by Russia coach Dick Advocaat he risked his international place without regular first-team football but the 27-year-old is finally beginning to make his mark at Stamford Bridge.Ancelotti relished Zhirkov's work to provide the cross from which Branislav Ivanovic could hardly miss to net the winner away to Blackburn Rovers at the weekend.Zhirkov moved to west London for £18m last year but saw his first-team chances restricted by a knee injury before he made an impression by scoring in the win at Spartak Moscow earlier in October.Ancelotti said "the goal at Spartak Moscow obviously improved his confidence. He is playing continuously now so he is showing some good football and he is working for the team."He was consistent last week against Wolves and he was consistent against Blackburn. Last season he showed he was ready when he replaced Ashley Cole. He is a very efficient player and I think he has a future."Source: Premierleague.com