Saturday will mark the first anniversary of Terry's decision to call time on his international career because of the fall-out from his race trial involving Anton Ferdinand.
Terry - who was acquitted of racially abusing Ferdinand in court - would normally be the kind of man England could count upon when it came to crucial matches in unforgiving places like Ukraine.
And the fact England have only kept two clean sheets - both of them against San Marino - suggests Roy Hodgson could do with the 32-year-old back in the international fold.
Reports last season suggested Terry was considering making himself available for international duty again, but Cahill is convinced that will not happen.
"That decision has been made. He has moved on now," Cahill said.
"I think that's done and dusted. That decision has been made and that's all history now. We know how well he did for his country and that's that."
Although almost a year has passed since Terry's retirement, Cahill thinks the Three Lions are still adjusting to life without the Chelsea skipper, and his former England partner Rio Ferdinand, who retired from England last season.
"They were two huge players and they retired at similar times so there had to be a transitional period and that's what it is at the minute," the Chelsea defender said.
"We have some quality centre-backs as well, but when two big names, two big top-class centre-halves come out of the set up there is that worry. People are always going to talk about it."
Following Terry's final game against Moldova, who England face this Friday at Wembley, Hodgson set about trying to find a settled centre-half partnership that he hoped would remain a constant throughout the World Cup qualifying campaign.
The England manager struggled to settle on a solid pairing at the start. Cahill, Joleon Lescott, Phil Jones, Chris Smalling, Phil Jagielka and Steven Caulker were all used in a variety of combinations.
Hodgson seems now to have settled on Cahill and Jagielka as his first-choice pairing after starting with the duo in England's last three matches.
Concerns have been raised about the partnership after Kenny Miller out-smarted Cahill at Wembley last month, but the Chelsea centre-back does not think defence is a weak point in the England side.
"It's obvious people are going to say (defence is a weakness) because of the names that have gone out, but people step in," said Cahill, who looks set to win his 17th cap on Friday against Moldova at Wembley.
"I don't think (it is a weakness). Ultimately, results will settle that talk
"When I was first in the set up I was a lot younger so I feel like I have improved and I feel like I can still improve."
Scotland striker Miller only had to throw the slightest of dummies to gain a yard on Cahill and then bury a low drive past England goalkeeper Joe Hart.
He acknowledges he should have done better that night, but he insists he has put the performance to the back of his mind.
"I haven't seen replays of it, but I have replayed it there," Cahill said, pointing to his head.
"You know straightaway when you make mistakes. You evaluate what you have done and then you move on."