Bolton Wanderers boss Sam Allardyce is aiming to make six signings in the summer.
"Some of the squad will come from free agents, some will be more heavily invested in," he told the Bolton Evening News.
"We have to get some younger players in.
"Most of our players are signed towards the end of July or even into August," he said, "but we always have to do a lot of business in June to set up those deals.
"Unfortunately, June's going to be a waste of time because of the World Cup. So it's important that we secure a few players before then.
"It just means we'll have to work extremely hard in the summer to try to sign the sort of players we need to continue our progress, with less funds than other clubs.
"But I probably work harder in the summer than any other manager in the Premiership, even though they wouldn't agree, and this time there's going to have to be a lot of work done to get in the five or six players I need."
"Some of the squad will come from free agents, some will be more heavily invested in," he told the Bolton Evening News.
"We have to get some younger players in.
"Most of our players are signed towards the end of July or even into August," he said, "but we always have to do a lot of business in June to set up those deals.
"Unfortunately, June's going to be a waste of time because of the World Cup. So it's important that we secure a few players before then.
"It just means we'll have to work extremely hard in the summer to try to sign the sort of players we need to continue our progress, with less funds than other clubs.
"But I probably work harder in the summer than any other manager in the Premiership, even though they wouldn't agree, and this time there's going to have to be a lot of work done to get in the five or six players I need."
