Japan head coach Jamie Joseph on Thursday backed his team to keep their cool in the first rugby Test against France despite temperatures forecast to soar to 35 degrees Celsius by kick-off time in Toyota on Saturday afternoon.Joseph made six changes from the side that thrashed Uruguay 43-7 last weekend for Saturday's "massive challenge" against Six Nations Grand Slam winners France.Three players have been ruled out because of Covid, with scrumhalf Naoto Saito, hooker Shota Horie and fullback Ryuji Noguchi all unavailable.Joseph admitted his players will find it tough to deal with the heatwave conditions that have seen record June temperatures in Japan this week, but believes France "will find it even more challenging"."We've got to keep the game as fast as possible and back our ability to handle the heat a little bit better," said Joseph as he named his team."No doubt France will have tactics and ways of trying to slow the game up so that they can get plenty of rest."Joseph brought World Cup veterans Wimpie van der Walt and Ryohei Yamanaka back into the starting line-up as Japan look to get some game time under their belts.Covid disruptions mean the 2019 World Cup hosts have played only eight Test matches since reaching the quarter-finals on home soil two-and-a-half years ago."It's a starting point for us," said Joseph."We're way behind in terms of Test matches together, and then that's compounded by the fact that some of our key players are out through injury."South African-born wing Gerhard van den Heever keeps his starting place after winning his first cap at the age of 33 and scoring last week against Uruguay.Centre Dylan Riley, who also scored against the South Americans, wins his sixth cap."Our game plan is to keep