Less than three years later, he was fired while standing over the smoldering ashes of a talent-poor, over-the-hill defense that ranked 31st in the league during his tenure.
Owner Mark Davis distanced himself from Allen back in February, making it clear there would be "no more excuses" for a coach handpicked by general manager Reggie McKenzie.
Inheriting a roster languishing in salary-cap hell, Allen must have realized he was facing long odds when he accepted a prestigious one of 32 NFL head-coaching jobs.
But that's an excuse.
Even if McKenzie's track record in selecting signal-callers would make Jerry Angelo and Lovie Smith blush, Allen exacerbated the problem by consistently mismanaging the quarterback room.
Once it became abundantly obvious even to casual football observers that Schaub could no longer convincingly throw beyond 10 yards much less drive the ball outside the numbers or down the seam, Allen attempted to pull the wool over his fanbase's eyes, claiming he had witnessed no loss of arm strength.
Allen is a trusted defensive mind and a good man, by all accounts. He will have an open invitation to rejoin the staffs of Fox and Payton.
As the public face of an NFL franchise, though, he was simply overmatched.