Manchester City wasted a chance to put pressure on Premier League leaders Chelsea as the champions crashed to a shock 1-0 defeat at struggling Burnley on Saturday.
Manuel Pellegrini's side would have moved within two points of Chelsea with a victory, but instead they departed Turf Moor with their hopes of retaining the title hanging by a slender thread after a lacklustre performance was punished by George Boyd's second half winner.
City remain five points behind Chelsea, who can extend that advantage to eight with a victory against Southampton at Stamford Bridge on Sunday.
To make matters worse for City, Jose Mourinho's side will still have one more game in hand after facing Southampton.
The dismal defeat, their first against Burnley since 1974, was the worst possible warm-up for City's Champions League last 16 second leg trip to Barcelona in midweek and added to the growing pressure on Pellegrini.
The third bottom Clarets took the lead in the 61st minute when Vincent Kompany's header only reached the edge of the penalty area, where Scotland midfielder Boyd drove a fine low left-footed strike past City goalkeeper Joe Hart.
City had a strong penalty appeal turned down in stoppage-time when Pablo Zabaleta tumbled under a challenge from Ben Mee.
"It was a normal performance and I don't think we played very badly. We created more chances, they had one shot on target and got a beautiful goal," Pellegrini said.
"But of course we're doing something wrong as we are not winning the games we normally do.
"When you have a mathematical chance, you have a chance to win the title. The reality is that it's more difficult to do so now."
Arsenal cemented their position in the top four as Olivier Giroud's blistering strike inspired a 3-0 rout of West Ham.
Arsene Wenger's third-placed side are aiming to qualify for the Champions League via a top-four finish for the 18th year in a row and they are well on course after a fifth successive league victory.
Giroud broke the deadlock seconds before the break as the France striker cut in from the right edge of the penalty area to lash an unstoppable left-footed shot into the far corner.
Wales midfielder Aaron Ramsey got Arsenal's second, and his first since December, in the 81st minute when he played a one-two with Giroud and finished with aplomb.
Mathieu Flamini came off the bench to seal the points with an 84th minute goal that lifted the Gunners four points ahead of fourth-placed Manchester United and six clear of fifth-placed Liverpool.
"It was a convincing win and a very important one as well. That's the kind of game we want to play," Wenger said.
"When it doesn't work it is questioned but that is the game we love."
Aston Villa's revival under new manager Tim Sherwood gathered pace as they boosted their bid to avoid relegation with a crucial 4-0 win at fellow strugglers Sunderland.
Villa had scored only four away league goals all season, but they have been transformed since former Tottenham boss Sherwood took charge and have now won their last two league games to climb above Sunderland, who drop to fourth bottom after their sixth consecutive game without a win.
Christian Benteke and Gabriel Agbonlahor both scored twice before half-time, prompting angry Sunderland fans to surround the bench to criticise boss Gus Poyet.
"A day like today (Saturday), you need to analyse very carefully as it's not acceptable. There is nobody to blame but ourselves," Poyet said.
"When you are a fan and you see your team performing like we did in the first-half, I would do the same."
Crystal Palace pushed second bottom QPR deeper into the relegation mire with a 3-1 victory over their London rivals at Selhurst Park.
Alan Pardew's side swept into a three-goal lead by half-time thanks to strikes from Wilfried Zaha, James McArthur and Joel Ward, before QPR's Matt Phillips produced one of the goals of the season in the closing stages.
Bottom of the table Leicester wasted a chance to improve their survival hopes as 10-man Hull held on for a 0-0 draw at the King Power Stadium despite Tom Huddlestone's dismissal for a second booking.
West Brom ground out a 1-0 win against Stoke at the Hawthorns, with the only goal in the 19th minute from Brown Ideye.
On Sunday, Manchester United host Tottenham and Everton face Newcastle, while Liverpool travel to Swansea on Monday.