London: Chelsea captain John Terry scored an own goal to gift Crystal Palace a 1-0 victory on Saturday, weakening the west London team's grip on the Premier League lead.
The veteran center back headed Joel Ward's cross past his own goalkeeper, Petr Cech, seven minutes into the second half at Selhurst Park.
Chelsea's first loss to Palace since 1990 means Manchester City could topple Jose Mourinho's side from the summit by beating Arsenal in the late game.
This was Chelsea's second successive away loss following a defeat at Aston Villa two weeks ago before beating Arsenal 6-0.
And this time there could be no grounds for Mourinho to complain about the referee. In fact, only Palace could have cause to grumble at Lee Mason's officiating, as twice in the space of two first-half minutes the referee rejected penalty claims when Gary Cahill challenged Cameron Jerome and then Yannick Bolasie.
Both might have been given in other circumstances but Palace, who were organised, resilient and dangerous on the counter-attack, put the incidents behind them to earn victory.
Tony Pulis' Palace had chances before and after Terry's mishap. Bolasie was unable to convert from a cross, while Jerome hit a post.
Palace goalkeeper Julian Speroni twice denied Eden Hazard, the second a fine save when the Belgium midfielder was through one-on-one.
But Palace ended a five-match winless streak with a much-needed victory that put them five points clear of the relegation zone.
In another match, Swansea beat Norwich for the first time in the Premier League, winning 3-0 with a brace from Jonathan de Guzman. It was the Welsh club's first win in 10 games and gave Swansea some much-needed breathing space above the relegation scrap.
Swansea had not beaten struggling Norwich in five previous league meetings but two clinical finishes from de Guzman plus a 75th-minute goal from winger Wayne Routledge ended that unwanted record at the Liberty Stadium.
Garry Monk's side dominated both halves and, but for some jittery moments after the break, never looked in trouble.
Jay Rodriguez scored twice as Southampton routed Newcastle 4-0 in a match between two midtable teams with little to play for.
Rodriguez started and finished the scoring, netting the opener just before halftime and then adding the fourth goal in the 89th, after Rickie Lambert and Adam Lallana had already made sure of the victory.
The win means Southampton leapfrogged Newcastle into eighth place with 48 points, but remains eight points out of the European places with six games to go.
Rodriguez, Lambert and Lallana are all hoping to make England's World Cup squad and boosted their chances with a high-scoring display.
Lambert's cross set up Rodriguez for the opener, and Lallana's goal was a powerful 25-yard shot.
Rodriguez also hit the post before netting his second.