Theodorakopoulos coached Everton's Australia midfielder when he was a 16-year-old with Belmore Hercules in New South Wales regional league - and saw then Cahill's capacity to rise to the occasion.
"You could tell he had something different," Theodorakopoulos told Reuters.
"He had the thirst to achieve and had no problem dealing with older players. He was not intimidated and he still has that same character now - the harder the opposition, the better he plays."
Everton fans will hope for more of the same against Chelsea at Wembley from Cahill, who has scored against all of England's so-called Big Four sides in the past two seasons - including a superb overhead kick equaliser in a 1-1 draw against the Londoners in 2007/08.
The man who snatched Australia's first World Cup finals win with two late goals against Japan in 2006 embodies the blend of skill and sheer commitment shown by David Moyes's side in reaching the final and finishing fifth in the Premier League.
FIRST HONOUR
Cahill, 29, is now hungry to end Everton's 14-year wait for a trophy.
"We need to believe we can win," he told a news conference in Liverpool this week. "We need to believe that once we cross that white line this is our chance of winning some silverware."
The FA Cup would represent the first major honour for Cahill, described by one Australian magazine last month as "our most important sportsman" for his exploits in the high-profile Premier League.
Growing up in Sydney's western suburbs, Cahill and his brothers Sean and Chris all showed a remarkable willingness to achieve according to Theodorakopoulos, who has coached all three siblings.
When he was 17, his parents - English father Tim and Samoan mother Sisifo - took out a loan to send him to England for a trial with Millwall.
Lucas Neill, his compatriot and ex-Millwall colleague, recalls Cahill making enough of an impression that after two days the club had already decided to sign him.
BARGAIN BUY
Cahill established a reputation as a goalscoring midfielder with the London club. West Ham United defender Neill said: "I gave him the nickname Timmy Shoot - every time he got anywhere near the goal, there was never any chance he was going to pass to anyone."
Cahill was also eager to learn. Les Briley, a youth coach with Millwall, said: "Every day he took on board information from coaches and he grew and grew all the time."
It was on Millwall's surprise run to the 2004 FA Cup final that Cahill achieved national prominence, scoring the semi-final winner against Sunderland. Although they then lost to Manchester United, it was one of the most magical days for the Australian.
Cahill was 24 when he stepped up to the Premier League in the 2004/05 season but showed immediately why his 1.5 million pounds fee was a bargain, hitting 11 goals as Everton finished fourth.
Former Eve
