Newcastle United have made Mauricio Pochettino question himself before.
Tottenham's now-infamous 5-1 defeat at St James' Park on the final day of the 2015-16 campaign cost them second place in the Premier League and launched a period of deep introspection for their manager. It was a moment of such desolation that Spanish journalist Guillem Balague chose it as the inauspicious starting point for his book "Brave New World," chronicling Pochettino in his own words as he began a journey that would take Spurs to a Champions League final just three years later.
In doing so, through a mixture of innovative high-energy football and powerful team spirit, all on a modest budget, the 48-year-old became one of the most sought-after managers.