Sinner, a key member of the Italian team which triumphed at the past two editions, elected to maximise his recovery during the sport’s brief six-week off-season after triumphing at last week’s ATP Finals.
The presence of just one of the top 10 men’s players at this year’s event has prompted discussion over the tournament’s future format.
But, after Berrettini and Cobolli starred for Italy in their quarter-final against Austria, both players spoke about the privilege they feel in competing for their nation at the Finals.
Berrettini maintained momentum from his opening straight-set win as he clinched an early break of serve and would not be caught after racing into a 3-0 lead.
The former Wimbledon runner-up, ranked 56th in the world, then broke immediately in set two after Collignon double-faulted twice.
However, his charge to the finish was slowed when Collignon took his first opportunity to level at 2-2 – and the Belgian was denied a fourth-straight game when Berrettini landed a sensational cross-court forehand to shut down another break point two games later.
But Berrettini would not lose his grip on the contest after reasserting himself with another break, serving out for his 10th consecutive singles win when playing for his country.
Speaking post-match, Berrettini said: “Pressure is a privilege. Obviously I feel the pressure, but you’re playing in front of your home country, my whole family is here, we are all great friends in our team.
“It is such a special feeling for me. I take the bad feelings away and just enjoy the moment.”