But he has returned to Conte's first XI for the past four matches and put in assured performances at the heart of the back three, a switch from the position on the left of the centre-backs that he filled during last season's Premier League title triumph.
It is that sort of pedigree that makes the 32-year-old an obvious pick for Southgate in Russia, according to Conte, who led Italy to the quarter-finals of Euro 2016.
"In this moment he's deserving to play," he told reporters ahead of Saturday's trip to Swansea City.
"He's in good physical condition. We are talking about an important player with great experience. He has played big competitions.
"I know when you have to go to play a World Cup or European Championship, it's important to have players with great experience because the pressure will become very strong for everyone.
"I'm sure that the coach will take the best decision for the national team."
Cahill remains Chelsea's captain, a role he took on full-time following John Terry's departure last year and Conte suggested a period of adjustment has been necessary in the club icon's absence.
"It wasn't simple replacing John Terry because we are talking about a great leader," he explained. "It's something you have in your blood.
"I think Cahill developed a lot this year, but we have three or four players who take responsibility, who try to lead the team."