Jürgen Klopp has urged the football authorities to relieve the burden on top players before it curtails careers after Trent Alexander-Arnold was ruled out for a defining few weeks in Liverpool’s quest for the quadruple with a hamstring problem. The Liverpool manager is perplexed why everyone accepted the situation where high-class footballers are at greater risk of injury than their peers because of their bigger workload as he revived calls for the use of five substitutes per game. Alexander-Arnold has been withdrawn from the England squad to face Switzerland and Ivory Coast and is set to miss Liverpool’s potential title decider against Manchester City and both legs of their Champions League quarter-final with Benfica. He may be in a race to play in a potential FA Cup semi-final and then to face Manchester United on 19 April. James Milner, who often deputises at right-back, has been ill and may sit out Sunday’s FA Cup tie at Nottingham Forest. Either Joe Gomez or the 18-year-old Conor Bradley could stand in, though Klopp accepted Alexander-Arnold was unique. “I don’t know any player who plays like Trent in the world so it will be difficult to find a one-versus-one replacement,” said Klopp, who confirmed Alisson would start but revealed Mohamed Salah was a doubt. Alexander-Arnold has played in 35 of Liverpool’s 46 games this season and they could face another 17, with Klopp wondering where they could be crammed in. He said: “The calendar is not made for a lot of success for the same team.” Klopp argued that football needed to do more to look after players as he criticised international teams for organising June friendlies and Uefa for thinking of expanding the European Championship. “In the summer where for the first time in ages there is no tournament, what do we do? We put in some games,” he said. “That is the world. Uefa plans a new tournament for 32 teams or 36 or 58. I didn’t know that Europe had that many countries but they all play at the Euros. “We just have to make sure we protect the most important ingredient of this game, and that is the players. “We just accept top-class players get injured more than other people. It really makes no sense. Games are getting more and more. “We have to make sure that these top-class players have a better chance to have a 15-, 16- or 17-year career without any major [injury]. In other contact sports, they all have long breaks. “Tom Brady [the NFL player] is in Manchester talking to Cristiano [Ronaldo]: he has had a four-month break. That is why he can play until he is 54 or whatever.” Sean Dyche, the Burnley manager, has said in the past that having five subs would benefit bigger clubs. Klopp said: “I don’t know how many Burnley players are on international duty. All the teams at the bottom of the table – I’m really sorry – they are now there with three subs and would be there with five subs. That has nothing to do with it. But it would help all the players. It is not for an advantage; it is a necessity.”