Pre-season friendlies can be notorious barometers for a team’s Premier League season — and Liverpool will be hoping that maxim holds true after this remarkable defeat by Leeds United in Chicago.On a patchy Soldier Field pitch, Andoni Iraola’s side were 2-0 up and cruising, courtesy of goals from Luke Chambers and Florian Wirtz, but three goals in 13 second-half minutes and a late fourth from Dominic Calvert-Lewin (his second of the match) turned the contest on its head, with Leeds winning 4-2.Our experts analyse the main talking points.Liverpool need defensive reinforcements — quicklyWith just three weeks until their Premier League campaign gets underway, Liverpool have still got plenty of transfer business to get done.There’s the ongoing pursuit of France winger Bradley Barcola, who will essentially be Mohamed Salah’s replacement if they can agree a fee with Paris Saint-Germain. Barcola would be a statement signing, but at the other end of the field the need for defensive reinforcements is acute.Iraola has had to rely on teenage centre-backs Ifeanyi Ndukwe and Mor Talla Ndiaye throughout this tour. Left-back Luke Chambers has also been pressed into duty in the middle.The situation has been made worse by the absence of captain Virgil van Dijk following the World Cup, the muscle injury Joe Gomez picked up in the first friendly in Nashville and the inactivity of new signing Jeremy Jacquet, who hasn’t been risked in the U.S. after feeling some discomfort in training. Giovanni Leoni and Conor Bradley are still recovering from long-term injuries.The youngsters have done well in the circumstances and credit to academy graduate Chambers, who spent the second half of last season on loan at Charlton Athletic.However, the manner in which Liverpool fell to pieces in the second half in Chicago laid bare the importance of needing to strengthen both at centre-back and right-back. They just don’t have sufficient depth for the challenges ahead.It was all far too easy for Leeds as Iraola’s side conceded four times in the space of 25 minutes. Liverpool were carved open when Brenden Aaronson pulled one back and they couldn’t stem the tide.Defending set-pieces was a glaring weakness under Arne Slot last season and it remains an issue, especially dealing with long throws. Calvert-Lewin was completely unmarked when he converted at the far post after a flick on from Rodon with Kostas Tsimikas guilty of ball watching.After Longstaff made it 3-2, Calvert-Lewin grabbed his second in familiar fashion as Liverpool were bullied from another long throw.