Modern players spend so much time looking at smartphones, it is making them less skilful on the pitch, says the new vision coach for England's national side.
Sherylle Calder is a South African vision expert hired by the rugby union to improve hand-eye co-ordination among England's players ahead of this year's Six Nations.
She said she had seen a deterioration across all sports over the six years in which phone use has rapidly increased.
"We have seen in the last five or six years when we assess elite players in different sports that there is a decline in skill levels," Calder told The Guardian.
"We are losing the ability to communicate well and all those skills are declining. We will be working really hard on awareness because awareness helps you make effective decisions under pressure."
Although players will be allowed to keep their phones for the tournament, they will be encouraged not to overuse them.
"We can't stop them but we will teach them good behaviours," Calder said.
"We develop skills by climbing trees, walking on walls and falling off and learning all those visual motor skills which people aren't doing any more," she added.
"Young kids spend a lot of time on mobile phones so those instinctive natural skills are disappearing.
"If you don't see something, you can't make a decision. So one of the skills we work on is being able to see, or pick up, something early. The earlier you see the more time you have to make a decision. That's a trainable skill."