Lleyton Hewitt says the returning Nick Kyrgios has been the ultimate team man during Australia's Davis Cup preparations and that he's mentally prepared.

Captain Lleyton Hewitt says his criticism the new-look Davis Cup stands as the tournament kicks off but the team is "going to lay everything on the line".

The new-look Davis Cup gets underway on Monday, with Australia kicking off their tournament against Colombia in the early hours of Wednesday morning.

Tennis's "big three" are still winning, but Boris Becker can see the gap closing as he prepares to captain Germany in January's ATP Cup in Brisbane.