... Victor Anichebe's late goal saw West Brom hold them to a 1-1 draw at The Hawthorns.
Branislav Ivanovic escaped his marker to fire home from a David Luiz set-piece delivery in first-half stoppage time, and that for a long time looked to have given Jose Mourinho's side a four-point cushion over second-placed Arsenal, who play Manchester United on Wednesday.
Premier League
1 Chelsea 57
2 Arsenal 55
3 Man City 54
4 Liverpool 50
5 Tottenham 47
6 Everton 45
7 Man Utd 41
8 Southampton 39
9 Newcastle 37
10 West Ham 28
11 A Villa 28
12 Swansea 27
13 Hull City 27
14 Stoke City 26
15 C Palace 26
16 Norwich 25
17 West Brom 24
18 Sunderland 24
19 Cardiff 22
20 Fulham 20
However, Anichebe headed past Petr Cech in the 87th minute to secure a valuable point for the struggling Baggies.
West Ham claimed a crucial win over fellow strugglers Norwich, with James Collins and Mohamed Diame both scoring late goals.
The Canaries created most of the better openings in the game but Collins arrived just in time to head home an 84th-minute chance - with Norwich goalkeeper John Ruddy culpable of coming to collect the delivery and getting caught out.
With the visitors chasing a late equaliser they were then exposed at the back, allowing second-half substitute Diame to wrap up the win late in stoppage time.
Jose Fonte's second-half strike saw Southampton extend their unbeaten run to six Premier League matches at Hull, who remain within touching distance of the relegation scrap.
Saints were good value for the 1-0 win, maintaining a fierce tempo throughout at the KC Stadium and creating a host of fine chances.
Rickie Lambert and Jay Rodriguez were both in profligate mood, raising Hull's hopes of a battling draw, but Fonte settled things in the 69th minute when he stabbed over the line at the second attempt.
Cardiff and Aston Villa played out a goalless draw which does far more good for the visitors' hopes of survival than their hosts.
Cardiff dominated the opening half and struck the woodwork through Fraizer Campbell and a deflected Craig Noone shot, but could not find the net.
Villa offered no threat during the opening 45 minutes but could have taken all three points had Leandro Bacuna and Gabriel Agbonlahor shown better composure in front of goal.
Ultimately this was a game Cardiff needed to win, and one Villa were happy enough to avoid losing, and there is no question this result will be more warmly welcomed by Paul Lambert than Ole Gunnar Solskjaer.
Villa climb five points clear of the drop zone, but Cardiff remain 19th with just two wins from their last 17 league games.