A Champions League final between Liverpool and Tottenham sums up the kind of unpredictability that shaped the 2018-19 European football season. From Real Madrid’s immediate decline in the first season without Cristiano Ronaldo to Barcelona’s spectacular choke in the Champions League for the second season running, there have been some surprising storylines across football’s first continent.While Liverpool under Jurgen Klopp provided more evidence of the Merseyside giants being back in the big time, some of Europe’s ‘superclubs’ showed they have an urgent need to rebuild.In Italy, Napoli, Roma, Milan and Inter have been given another reminder of the gulf between them and Juventus. In Spain, Madrid rivals Real and Atletico are facing busy summers ahead as they try to bridge the gap with league champions Barcelona. The Catalan giants themselves will be seeking reinforcements on the back of their Champions League disappointment and the arrivals of midfielder Frenkie de Jong, and possibly defender Matthis de Ligt, from Ajax, could go a long way in making them champions of Europe again. Bavarian giants Bayern Munich have faced a difficult season and despite the successful defence of the Bundesliga title, manager Niko Kovac will be aiming to overhaul an ageing squad. Rivals Borussia Dortmund too will look to strengthen after their title collapse. In England, Arsenal, Chelsea, Tottenham and Manchester United have shown they don’t have squads capable of challenging for the league title yet.But among the ‘superclubs’ of Europe, it is perhaps United, Real and Bayern who need an urgent revamp this summer.United’s woesUnited, in particular, have regressed the most. After a second-place finish in 2017-18, United finished sixth in the Premiership and failed to come close to any cup final.After Jose Mourinho’s sacking in December, Ole Gunnar Solskjaer’s smooth start to life as United manager was quickly soured by a poor run of results that culminated in them winning just two of their last 12 games in all competitions. It was a train-wreck of an end to the season and ruthlessly exposed the club’s frailties; United, and club chief Ed Woodward in particular, will look to quell rising anger among fans with heavy investment in players.Six seasons of an ambiguous recruitment policy following the retirement of Alex Ferguson have seen United spend €895 million in player signings without any significant return on the pitch. Making it worse for United’s fans is the success of Manchester City who haven’t spent much more.Solskjaer is the fourth full-time manager at Old Trafford since Ferguson and the summer transfer market will bring flashbacks of similar rebuilding attempts under Louis van Gaal in 2014 and Mourinho in 2016.However, with a number of problem areas in the squad, Solskjaer faces the unenviable task of making United competitive again domestically and in Europe.The club already has two positions to fill in central midfield following the departures of Marouane Fellaini and Ander Herrera. Lack of quality options on the right flank too has affected United last season.Ashley Young and Antonio Valencia, both winger-turned-fullbacks, have been regularly used as right backs in recent years, with the latter laying claim to the starting role last term. With Valencia leaving and Young offering little offensively, Solskjaer will be seeking a more effective option this summer. The club will also be looking for a right winger after the likes of Marcus Rashford, Jesse Lingard, Juan Mata, Diogo Dalot, Alexis Sanchez and even Romelu Lukaku were asked to chip in for want of a more conventional option. However, the most important position where the club will be looking to bring a big name is inarguably at centre-back. Failure to bring an established star for the position last term caused an irreparable breakdown in the Woodward-Mourinho relationship.To make matters worse, there remains an uncertainty over the future of star midfielder Paul Pogba and four-time club player-of-the-year David de Gea.In a word, United need to find players in every possible position, and fight to retain key members of the current squad. With the summer transfer window ending on August 8 in England, that will need some quick, decisive moves.Real messZinedine Zidane’s return to football management after a short-lived sabbatical surprised many. This time, Zidane faces a far tougher task than during his first stint in 2016. The primary reason being the need to overhaul Real’s ageing squad. Of the core of the squad that won the Champions League four times in five years, Ronaldo is no longer at the club while Sergio Ramos, Marcelo, Luka Modric, Karim Benzema and Keylor Navas are in their 30s. Welshman Gareth Bale is also set to leave the club.Real’s underwhelming season exposed the club’s heavy reliance on an ageing core and their failures this time only highlighted the urgency needed to bring in players for the long-term. With names like Eden Hazard and Paul Pogba being linked to the club, it is no secret that Real will be going all out in the transfer market this summer. A centre-back and a central midfielder will be targeted by Real but the priority is likely to be a creator in the Hazard or Pogba mould.The 13-time European champions will also need a goalscorer to fill in the void left by Ronaldo, who went to Serie A champions Juventus. It remains to be seen whether Zidane opts for an orthodox No. 9 to replace Benzema or brings in someone to complement the French forward.Bayern’s rebootBayern’s problems are similar to those of Real. Manuel Neuer, Mats Hummels, Javi Martinez, Robert Lewandowski, Rafinha and Jerome Boateng are in their 30s with Thomas Muller months away from stepping into his fourth decade.The ageless Arjen Robben and Franck Ribery announced their departure after leading Bayern to yet another Bundesliga title. Rafinha is also on his way out.The club’s fullbacks also had ordinary seasons but Bayern have already made their move for those positions, signing Benjamin Pavard and Lucas Hernandez.Wingers and central defenders will also be sought this summer with Leroy Sane expected to be among the top targets.The club’s struggles last season were papered over by the Bundesliga triumph so Kovac will be under pressure again to deliver in Europe.After a season plagued by under-investment in their ageing squad, Bayern have been quick in signing fresh players. How far that goes in improving their fortunes in the Champions League could decide Kovac’s fate.