LONDON – Manchester United and Tottenham suffered shock home defeats by Crystal Palace and Newcastle as Liverpool and Manchester City laid down another marker that they seem set to do battle for the Premier League title again this season.Liverpool’s 3-1 win at Anfield was a reality check for Arsenal, as Jurgen Klopp’s men maintained a two-point advantage over City, who were also 3-1 winners at Bournemouth.Below the top two, the other four of the “big six” have already suffered defeat this season, but Chelsea did pick up their first win under Frank Lampard in thrilling fashion, 3-2 at Norwich.Here, AFP Sport takes a look at three things we learned in the Premier League this weekend:UNITED REBUILD A WORK IN PROGRESSLost amid the condemnation of the social media trolls who racially abused Marcus Rashford on Saturday was the stark reality that Crystal Palace’s shock 2-1 win at Old Trafford showed Ole Gunnar Solskjaer’s overhaul of Manchester United remains some way from completion.Jordan Ayew’s opening goal for Palace exposed the flaws in Solskjaer’s defence even after the combined £130 million ($160 million) spent on adding Harry Maguire and Aaron Wan-Bissaka to the back four.United striker Rashford’s costly penalty miss sparked the racist jibes, but it was possible for United to have survived that mistake after Daniel James curled in his second goal for the club in the 89th minute.However, emphasising United’s creaky foundations, Palace defender Patrick van Aanholt was able to find space to shoot past David de Gea’s dismal attempted save in stoppage-time to hand Solskjaer’s team their first defeat of the season.While it is far too early to panic, United have only one win from three games and it is questionable whether they have banished the defence lapses and lack of cutting edge up front that undermined them last season.LUIZ SHOWS ARSENAL’S LONG ROAD AHEADArsenal also headed to Liverpool filled with early-season optimism after two wins to start the campaign and a seemingly fruitful transfer window.Club-record signing Nicolas Pepe made his first start at Anfield and demonstrated the trickery and pace that should see him form a fearsome front three alongside Pierre-Emerick Aubameyang and Alexandre Lacazette.However, the difference between the sides is that Liverpool’s own stunning attacking trio of Mohamed Salah, Roberto Firmino and Sadio Mane, is backed up by arguably the world’s best defender in Virgil van Dijk.By contrast, Arsenal left adding a much-needed centre-back till the end of their summer shopping and David Luiz’s deficiencies were cruelly exposed as he conceded a stupid penalty for a shirt tug on Salah before being embarrassed by the Egyptian for Liverpool’s third goal.There are plenty of similarities between the current Arsenal and Liverpool prior to Van Dijk’s signing for a then world-record fee for a defender in January 2018.Since then, Jurgen Klopp’s men have won the Champions League, reached another final and came within a point of winning the Premier League last season.A similar upgrade is needed for Arsenal to make the leap.TOO HIGH A BAR FOR VARThe Premier League set its stall out not to overturn subjective refereeing calls using VAR for its introduction to English football this season unless a grievous error has been made by the official on the pitch.That has certainly been the case for penalty appeals.City were denied a strong claim against Spurs last week when Erik Lamela wrestled Rodrigo to the floor, whilst both the champions and Tottenham were left bewildered when they were not awarded spot-kicks on VAR reviews on Sunday.Harry Kane and David Silva were taken out by opponents, who did not play the ball, yet the original call of no penalty stood.However, offsides and handball decisions are not being judged on the same criteria and are therefore far easier to overturn.The two-tier system is proving confusion to players, coaches and fans with no one clear what “clear and obvious error” means.