One juror said "balls", directed by MJZ's Nicolai Fuglsig, had scored more points than any other film in the longlist judging stage.
However, the film faces stiff competition from a number of gold Lion contenders in a category that is described by jurors as the strongest for years.
"Balls" failed to win the top prize at either the British Television Advertising Awards or the US One Show and Clios. The ad was awarded two yellow Pencils at the 2006 D&AD Awards, but failed to win a coveted black Pencil.
Some observers also predict that Fallon's Grand Prix in the outdoor category for Tate Britain may work against ultimate glory for "balls".
Other strong contenders include Abbott Mead Vickers BBDO's "noitulove" for Guinness and Wieden & Kennedy London's "impossible dream" film for Honda.
Guinness won Best in Show at the Clios in May, while Honda won the Grand Clio and was named the best ad at the BTAA Awards.