Chelsea's remarkable unbeaten home record in domestic matches has reached three figures - double figures is normally sufficient cause for celebration - but the numbers mask a trend that has undermined their past two title campaigns. Instead of a fortress, Stamford Bridge is more of a community centre where points are shared generously with visiting teams.

While Chelsea's penalty shoot-out defeat by Charlton Athletic after a 1-1 draw in a League Cup tie in 2005 leads some to have reservations about their century claim, there is no disputing that they have not lost in their past 80 league matches. Yet, increasingly, that sequence is being extended by damaging draws, the latest one conceded to Wigan Athletic on Monday.

Chelsea's unbeaten run began under Claudio Ranieri's reign as they recovered from a 2-1 home defeat by Arsenal in February 2004 that left their opponents on course to become champions. It continued through the next two seasons as José Mourinho won back-to-back titles and by December 2006 the club's supremacy at Stamford Bridge was such that their 51 undefeated league games comprised 42 wins and only nine draws.

Since then the record has remained, although there has been a subtle but significant change. The subsequent 29 league matches have brought 17 wins and 12 draws, a rate of fewer than 1 wins per draw compared with more than 4 wins per draw previously. Wigan followed Blackburn Rovers, Fulham, Everton, Aston Villa and Liverpool in taking a point from Stamford Bridge this season, while from December last term Chelsea were held at home by Arsenal, Reading, Fulham, Bolton Wanderers, Manchester United and Everton.

The contrast with Manchester United's home league record in that period is stark. United have not been unbeaten at Old Trafford, but their two defeats in the equivalent 29 home league matches have been accompanied by 25 wins and two draws, giving them 14 more points than Chelsea.

The charge that Chelsea have been punished for not trying to kill off matches under Avram Grant - or perhaps simply for not being able to do so - is compelling. Five of the nine home league wins overseen by the Israeli have come by one goal, the latest against Middlesbrough last month, when the away team went desperately close to a late equaliser. Grant was not so lucky against Wigan.

Ton up:

Chelsea are unbeaten in 100 domestic home games: 80 league, 12 FA Cup, eight League Cup, the last including a defeat on penalties by Charlton Athletic.

Feb 2004 to Dec 2006: Chelsea went 51 league games unbeaten (42 wins, nine draws). Dec 2006 to present: 29 league games unbeaten (17 wins, 12 draws).

Previous longest run in top flight: Liverpool, Feb 1978 to Dec 1980, 63 matches (49 wins, 14 draws).