Captain Anne Keothavong credits strong camaraderie for Great Britain's run to the semi-finals as Raducanu and Boulter forge a close bond ahead of a key clash with Slovakia.
The 23-year-old Italian caps a historic year with his first ATP finals title, becoming the first player since 1986 to win the tournament without dropping a set.
Carlos Alcaraz fights through illness and a tough second set to beat Andrey Rublev, while Alexander Zverev beats Casper Ruud to keep semi-final hopes alive.