The visual skills expert, nicknamed 'Eye Lady' in the past, was drafted in by boss Eddie Jones earlier this week to help with preparations for the upcoming Six Nations.
Calder was a part of Sir Clive Woodward's backroom staff in 2003 when England lifted the Webb Ellis trophy, while also working closely with Pakistan batsman Saeed Anwar and four-time Major-winning golfer Ernie Els.
Ahead of Tuesday's warm-weather training camp in Portugal, Calder has warned England's players to ditch their mobiles so that full focus can be on the task at hand.
"In the modern world, the ability of players to have good awareness is deteriorating because of mobile phones," Sky Sports News quotes her as saying. "We will be working hard on awareness, which helps you make effective decisions under pressure.
"If you don't see something, you can't make a decision. We're going to work on skill levels and making good decisions under pressure. 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.
"When you look at your phone, you're losing awareness. There are no eye movements; everything is static. We are losing the ability to communicate. All those skills are declining."
Calder also has experience of working with the South Africa rugby team and has previously acted in an advisory role for Premier League club Bournemouth.