Rob Key, England men's managing director, spoke to the players selected in their provisional World Cup squad on Monday to tell them that they had been picked, and told those involved in the IPL that they will not be available for the knockout stages. The play-offs run from May 21 until May 26, clashing directly with England's Pakistan series.

ESPNcricinfo understands that players will be expected to return to the UK on the weekend of May 18-19, which could rule them out of their respective franchises' final group-stage fixtures. The group stage runs until May 19 and England are keen for their World Cup squad to have a few days together before their first T20I since December.

"You can't just call people back for no reasons: there are protections," Key said on Tuesday after announcing England's provisional squad. "Without injury or England commitments, we couldn't say to Phil Salt, for example, come back and have a rest for the next 15 days. But there is a window just before an England series when you can bring players back for England duty or injury."

Key revealed that Buttler, who has hit two centuries for table-topping Rajasthan Royals, had instigated the decision to come home before the end of the IPL. "I asked him very early on in the piece and said, 'Look, as England captain, you're obviously going to have this series against Pakistan. How do you see it?' And straightaway, he said, 'No, no, I want to come back and start getting ready for the World Cup in that series that's just before it.'

Buttler and his wife Louise are expecting their third child next month, so he may miss the start of the Pakistan series on paternity leave regardless. "When the due date is and when the baby comes is slightly fluid," Key said. "But whatever happens, I think you put your family first and make sure you're at the birth of your child. We'll cross that bridge when we come to it."

Key told players when they left for India: "Look, there is a good chance that you'll be coming back [early]," he said. "There is a chance you could stay out there. We may feel that if you get through to an IPL final that, maybe, that's the best thing to do. It might be that if there's only one of you then you'd let you go on and do that we have to keep it pretty fluid."

But he said that England's management decided the Pakistan series would help them to find clarity in the players' roles ahead of their opening T20 World Cup fixture, against Scotland on June 4. "We've got to the point where actually, we think it's more important that you come back and that group gets together: the likes of Phil Salt, opening the batting for England, getting that role going with Jos Buttler.

"You just want them to get together and spend a bit of time and build up to it. So much of what our white-ball team has done has been turning up a couple of days before and, bang, we're into a series, whereas I think that Pakistan series is going to be important for that, so they'll all come back ready for that.

"You want people to really start understanding what their roles are, what your best XI is going to be, and that's what we want to make sure: when we hit Barbados, we know exactly what that is. Last time, for the [50-over] World Cup, Adil Rashid was injured in that series versus New Zealand and we probably didn't take into account how much, when he came back, that altered the balance."

Other boards' approach to clashes between T20I series and the IPL play-offs have varied. New Zealand fielded a second-string team in Pakistan earlier this month, while the BCB have pulled Mustafizur Rahman out of the IPL early for a series against Zimbabwe. CSA will allow their players to stay in India for the play-offs, despite a clash with a three-match series against West Indies.