Frank Lampard steered Chelsea to a 2-0 win over Portsmouth while Arsenal's Champions League hopes for next season suffered a bodyblow with a 1-0 defeat at Blackburn Rovers on Saturday.
England midfielder Lampard slotted home the breakthrough goal for the champions at Stamford Bridge after 65 minutes and Dutch winger Arjen Robben made sure of the points with their second on 78 minutes.
The laboured victory on a heavy pitch, just three days after their Champions League loss there to Barcelona, extended Chelsea's lead at the top over Manchester United to 15 points.
Arsenal, who beat Real Madrid 1-0 away on Tuesday, failed to close the five-point gap on north London rivals Tottenham Hotspur in the race for next season's Champions League after Norway's Morten Gamst Pedersen got the only goal at Ewood Park.
Birmingham City beat Sunderland 1-0 in their relegation scrap with an Emile Heskey goal and Charlton Athletic were held to a 0-0 draw at home by Aston Villa.
Chelsea looked jaded after their 2-1 defeat by Barcelona and took their time warming up against Harry Redknapp's side, who now look firm candidates for the drop.
Ivory Coast striker Didier Drogba lined up the precious opener for Lampard, with the England midfielder making up for what had been a disappointing performance with a fine finish.
Robben did the same after being set up by a superb ball over the top of Portsmouth's defence by Icelandic striker-cum-midfielder Eidur Gudjohnsen.
The win lifts Chelsea to 69 points, well clear of Manchester United (54), who face Wigan Athletic in Sunday's League Cup final in Cardiff. Third-placed Liverpool, on 51, play Manchester City amidst Sunday's league games.
The big loser on Saturday was clearly Arsenal, who suffered their eighth away league loss of the season and squandered their game in hand on Tottenham in the race to finish fourth.
Spurs hold that slot with 46 points, while Blackburn's victory means they leapfrog Arsenal into fifth place on 43, leaving Arsene Wenger's side sixth on 41 and under threat by West Ham United, who also have 41 and a game in hand.
Premier League action was continuing with Saturday's late kickoff between Newcastle United and Everton.