The teenage midfielder has yet to complete a medical or sign a contract but broad agreements over the transfer fee – an initial £13million plus a further £7m in add-ons – and a five-year deal are now in place.

Chelsea are poised to beat Premier League rivals Newcastle in the race to sign Santos, one of the most highly-rated young players in Brazil.

It follows the Blues already agreeing a January deal for Ivorian striker David Datro Fofana, who completed his medical yesterday after an £8.6million fee was agreed with Norwegian club Molde.

Both signings are seen as players for the future by Chelsea. That could mean both Santos and Fofana quickly moving back out on loan in the January transfer window along with American goalkeeper Gabriel Slonina, who is now training with the club after his £12m summer switch from Major League Soccer (MLS) side Chicago Fire.