There was a time when Chelsea were one of the most imposing teams in the Premier League. They paid attention to height and could count on tall players such as John Terry, Branislav Ivanovic, Didier Drogba, Gary Cahill and Michael Ballack to provide aerial dominance at both ends of the pitch. Not any more. If size matters, nobody seems to have told Chelsea. They have conceded from headers in the past four games and Mauricio Pochettino is worried about his side’s lack of stature. It could be a problem when Chelsea travel to Goodison Park on Sunday to face Everton, who have the tallest squad in the top flight. “We need to be more aggressive,” Pochettino said on Friday. “When you create a team, you need to, in the Premier League, pay attention to this [height]. Of course it’s not that we will defend better if we have taller players, but I think the balance is important.” The obvious comparison to make is with Arsenal, Liverpool and Manchester City. They have solid spines. Arsenal’s centre-backs William Saliba and Gabriel Magalhães are more than 6ft and Mikel Arteta’s starting XI is usually packed with height. Declan Rice, the £105m midfielder, is 6ft 1in. The full-backs Ben White and Takehiro Tomiyasu are tall. Kai Havertz, the attacking midfielder, is 6ft 2in. It is clear that Arteta has focused on strengthening Arsenal’s centre. Pep Guardiola, too, has not packed his City side with tiny midfielders. The treble winners have brawn and beauty. The six-footers in their best XI include the centre-backs John Stones and Rúben Dias, Rodri in defensive midfield and Erling Haaland upfront. Every successful side needs a bit of elevation. Liverpool’s main centre-backs, Virgil van Dijk, Ibrahima Konaté and the injured Joël Matip, are tough to beat in the air. In midfield, Dominik Szoboszlai and Ryan Gravenberch are more than 6ft. Darwin Núñez, the striker, is 6ft 2in. The mind goes back to the days when Chelsea could rely on Drogba, their powerhouse striker, to help out at defensive set pieces. Now, though, Chelsea are being bullied. And if you go through Pochettino’s favoured XI, you will find an alarming lack of height among the outfielders. Reece James, the right-back, is 5ft 10in. Thiago Silva, who always starts in central defence, is 5ft 11in. The midfielders Enzo Fernández, Conor Gallagher and Moisés Caicedo are all less than 6ft and can be overpowered in the air. Raheem Sterling is 5ft 7in. And assuming the 5ft 10in Christopher Nkunku’s impending return to fitness sees him replace the 6ft 2in Nicolas Jackson up front, that leaves the 6ft 2in Levi Colwill at left-back, the 6ft 3in Axel Disasi in central defence and the 6ft 2in Cole Palmer on the right wing. Of course, this is not an exact science given that Chelsea have recently scored from headers against City and Brighton, and Arsenal conceded twice in the air against Luton on Tuesday. Chelsea have been considering the issue. Although they may need to bring in more height, the data shows they are winning a lot of first contacts at set pieces. Even so, frailty was evident when the unchallenged Nayef Aguerd headed in a James Ward-Prowse corner during West Ham’s win over Chelsea in August. As a former centre-back, Pochettino must be infuriated. In October Chelsea conceded an equaliser against Arsenal when Bukayo Saka was allowed to cross for Leandro Trossard to volley home. That was followed by Ethan Pinnock rising at the far post to head in a deep cross when Brentford won at Stamford Bridge a week later. It has been too easy. In Chelsea’s past four games they have conceded headers to City’s Manuel Akanji, Newcastle’s Jamal Lascelles, Brighton’s João Pedro and Manchester United’s Scott McTominay. Akanji and Lascelles were unmarked in the centre, and McTominay overpowered Colwill before meeting Alejandro Garnacho’s cross during United’s win over Chelsea on Wednesday. “It is unbelievable,” said Pochettino, who has identified collective failings. “During the last week we were working on this type of situation. I think two things are important to know. We didn’t put pressure on the crosser. Then with the quality of the Premier League that we all have, if the ball is there it is difficult to stop. “We need to improve. Conceding in this way, maybe I am not showing too much emotion, but I am really upset. We need to work much, much better in these situations.” Pochettino is looking for a greater work rate from his wide players. “It is both organisation and desire,” he said. “For me, we need to stop the crosses. Because after if it is: ‘Oh, it’s not my problem because the opponent crossed’ then for the defensive line it is so difficult to defend these type of situations.” Everton, who have not conceded a header this season, will be preparing the aerial barrage. Sean Dyche was at Old Trafford to see Chelsea lose to United. He will be telling James Tarkowski, Jarrad Branthwaite and Dominic Calvert-Lewin to be ready to attack those set pieces.