Robert Sanchez's second-half gaffe and a VAR error cost Brighton a deserved win at Crystal Palace as the Seagulls' winless run against their rivals extended to a seventh match
Brighton arrived at Selhurst Park intent on maintaining their unlikely challenge for the Champions League places, and should have left with all three points after thoroughly outplaying their hosts, with Roberto De Zerbi saying after the game: "There was only one team on the pitch
"And the PGMOL has apologised to Brighton after admitting the VAR made a mistake in disallowing a first-half Pervis Estupinan goal for offside, with the lines drawn incorrectly by officials
A Brighton club spokesman said on Sunday: "As was confirmed to the club by PGMOL last night, a serious error was made in disallowing Pervis Estupinan's goal
 The lines drawn in the VAR room to determine whether Pervis was in an offside position were drawn incorrectly, and the goal should have stood
 While hugely disappointed by the error, the club's accepted PGMOL's apology and will not be making any further comment
"Solly March finally gave De Zerbi's dominant side the lead midway through the second half, but their advantage only lasted six minutes before Sanchez dropped a cross under no pressure, allowing James Tomkins to head in the equaliser from close range
The defender's goal ensured Palace avoided a fourth defeat in six Premier League matches - but Patrick Vieira's team have claimed just three points in that time and their underwhelming form means they are just seven points clear of the relegation places
Brighton probably could not have picked a better time to travel to the home of their biggest rivals and attempt to end their four-year run without a win in the fixture
Palace have won just once in all competitions since November 6 and started the game on the back foot, with Vicente Guaita forced into two smart saves from the returning Alexis Mac Allister
Playing alongside the recalled Moises Caicedo and Pascal Gross in a midfield three, the Argentinian World Cup winner helped Brighton to control the encounter in impressive fashion
But they were still goalless at half-time after Kaoru Mitoma was denied his sixth goal in nine games by Guaita, while Estupinan’s looped strike was incorrectly ruled out for offside
Palace were not entirely without threat during the opening period, with Adam Webster producing two excellent blocks to keep out Jean-Philippe Mateta
But Brighton eventually opened the scoring in the 63rd minute when Estupinan’s brilliant right-wing cross caught Tyrick Mitchell napping, with March stealing in to volley past Guaita
The Palace fans began to voice their frustration as Brighton continued to dominate, but their angst turned to glee just moments later when Tomkins pounced on Sanchez’s error
There was only one team that looked like claiming a late winner, but Brighton were wasteful in front of goal, with Mac Allister guiding a free header wide and then volleying straight at Guaita as Palace just about held on
De Zerbi hailed Brighton's display as their best during his five-month spell in charge, but admitted he was disappointed not to have ended their wait for a win over Palace
"We are frustrated," said the Italian
 "We are sorry to lose two points
"There was only one team on the pitch but the reason is Brighton played a fantastic game - one of the best games with me
"But football is like this
 You can have a lot of chances to score, but with only one cross you can concede a goal
"De Zerbi also refused to criticise Sanchez, saying: "It’s not a problem
 He’s a very important player for us
"OK, he made a mistake today, but other players made mistakes when we could score
"After watching his side get outplayed at home, Vieira admitted he was "really happy" to have seen Palace come out of the contest with a draw
"I am satisfied with a point," said the Eagles boss
 "I think the game was really challenging for us, really difficult
"I thought Brighton were excellent today
 We needed to be more organised, well-disciplined defensively not to give them space that they needed to express themselves
"I'm really happy with the organisation that we had today and the discipline that we showed, because that allowed us to get into the game
 I am really happy with the point today
"It is important for us and the fans not to lose the derby game, but you have to recognise the quality of the team that we played against today
 I can understand that their manager can be frustrated because they created a lot of chances
"It’s often said the mark of a top goalkeeper is the ability to maintain concentration even when they have little to do
 In that respect, Sanchez fell way short of the mark at Selhurst Park
The Spaniard made no saves against Palace - a demonstration of Brighton’s dominance - but handed them an undeserved point with his clanger
Of course, a ‘keeper’s job is not just about making saves anymore, and Sanchez is a vital part of Brighton’s attacking game thanks to his skill with the ball at his feet
Remarkably, he completed 100 per cent of his passes in south London, and his figure of 27 completed passes was more than every single Palace player
But he failed in his primary task of keeping the ball out of the net and, in doing so, cost Brighton the three points they so clearly deserved
The alarm bells may not be sounding, but there should be grounds for concern about how the second half of this Premier League season is going to play out at Selhurst Park
Vieira helped Palace make positive strides during his first campaign in charge, including introducing a style of play that was easier on the eye for the regulars in south London
But his second campaign has seen Palace regress into a side that struggles to get anyone out of their seat, and they recorded just a quarter of possession as they were passed off the pitch by Brighton
Vieira was right to be pleased with a point given that - with the exception of the goal that was handed to Tomkins - they failed to record a shot on target
Palace now have just four goals in nine games across all competitions since the World Cup and only Bournemouth have a lower expected goals total than the Eagles in the Premier League this season
Seven points separates Palace from the bottom three - but with Manchester City, Arsenal and Brighton again looming on the fixture list, it wouldn’t be a huge shock to see Vieira's toothless outfit dragged into the relegation scrap
 are back at Selhurst Park next weekend when hosting  on Saturday; kick-off 3pm
 return to the Amex to host , also on Saturday; kick-off 3pm
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