McGuinness coached Donegal to a long-awaited All-Ireland title in 2012 and yesterday he led the county to an unlikely second final in three years, with Dublin their victims at the semi-final stage. Donegal had been available at 7/1 before the game.
Three years ago, at Dublin's Croke Park, McGuinness' players strangled the life out of the game's most resource-rich county at the same stage, but lost eight points to six - a record low score for an All-Ireland semi-final.
This time they turned on the style, scoring three goals to thrash the reigning champions by a margin of six points, 3-14 to 0-17.
The last time they reached the game's September showpiece, in 2012, Donegal defeated Mayo and this year they will go on to face Kerry, another historic football powerhouse, on September 21.
McGuinness was hired as a performance consultant by Neil Lennon in the wake of Donegal's 2012 success and his work at Lennoxtown has frequently been met with speculation that his double jobbing had been detrimental to Donegal, especially after they fell heavily to Mayo at the semi-final stage of the All-Ireland last year.
The 41-year-old confounded those criticisms yesterday, reinforcing his reputation as one of Gaelic football's most astute managers and most powerful motivators.
When Lennon, who had closely followed McGuinness' Gaelic Athletic Association career, left Celtic at the end of last season there were inevitable doubts about McGuinness' continuing role at the club. But Ronny Deila, who was already an acquaintance of the Donegal manager, took the unexpected step of inviting him to take even more responsibility in first-team matters, whereas Lennon had asked him to work mainly in preparing academy graduates for life in the senior game.
Asked in July how he planned to use sports science in forming his backroom operation, Deila said: "We already have a sports psychologist in Jim McGuinness, so I want to bring him in even more. All my staff's knowledge is going to be used, I can't do it all."