For some Derry fans at Healy Park, it was hard to believe.
One bemused supporter, with a camera around their neck, stood pitchside and spoke quietly.
"After all the suffering they've caused us..."
The "us" could only be Tyrone; All-Ireland and Ulster champions and the side who, more than any other, have tormented Derry in the seven long years since their last victory in the Ulster Championship. The display on Sunday was a huge contrast to that half-decade plus in the wilderness.
The Oak Leafers dominated the champions on their own turf. Derry played with technical accuracy, pace and total physical dominance.
They never trailed after opening the scoring in the fourth minute, and at times they had double Tyrone's own count. The first half was particularly impressive. Derry defended brilliantly and broke with real menace every time they won a turnover.
The half-back line was electric, with Gareth McKinless sparking forward repeatedly past an increasingly worried-looking Tyrone team.
Their defensive efforts kept the Sam Maguire holders to just four scores in the first period.
This feat was built on top of their dominance of the middle of the park. Derry seemed first to every kick out and breaking ball. Their players had more options when they got the ball, and a better idea of what to do with it when they got within range of the posts.
A lot of what Derry did right started with Conor Glass in the midfield even before Brian Kennedy's dismissal.
Tyrone just couldn't live with Glass' vision, pace and control of the football.
These are surely the moments Glass returned from Australia for. A player of his ability and athleticism could've had a successful professional career in the AFL.
Instead, he has returned home and taken part in what may be a defining moment for Derry GAA.
Because Sunday was not a freak performance. Derry have been building towards this from when they started their league campaign with a dominant victory over Down.
Manager Rory Gallagher has produced one of the best coached and organised sides in the country.
Derry played with a calmness and intelligence in defence that belied their youthfulness. They were surely helped by the constant orders from Gallagher, whose bark could be heard in the farthest corners of the ground.
This is a team that, unlike some Derry sides in recent decades, really believes in itself.
Indeed it was the players and management who were the most grounded amidst the celebrations following the final whistle.
Man of the Match Conor Doherty seemed relaxed as he spoke to the press after full-time, keen to stress the challenge of facing Monaghan in the semi-finals.
The coach just about had enough voice left to speak to the cameras post-match, where he admitted to thinking that Tyrone seemed a bit undercooked in their own first-round game against Fermanagh.
Tyrone will have plenty of time to ponder those words as they wait for the qualifiers to begin later in May.
The All-Ireland Champions looked entirely unlike themselves on Sunday. Their defence was leaky, their discipline was shaky and their attack was non-existent.
By the final ten minutes of the game, as Tyrone chased an unassailable Derry lead, the Red Hands were reduced to launching balls into the D.
In a summation of their frustrating afternoon, Niall Morgan shanked a 45 into the far right corner of the field.
It was the last in a sequence of bad kicks by Morgan, who endured an uncharacteristically poor game distribution-wise.
Tyrone didn't lack for fight, but couldn't channel it effectively. They tried to front up to Derry in the first half but ended up giving away free kicks.
Kennedy's moment of petulance that saw him sent off was mirrored in the second half by the needless ball-throw that got Conor McKenna his second yellow.
This performance was indicative of a Tyrone team who have not found consistency in 2022.
The side who ran the gauntlet of Cavan, Donegal, Monaghan, Kerry and Mayo to win their first All-Ireland since 2008 was a model of focus and high performance.
This group has lost 8 members of that panel but the heart of a championship team is still there.
They ended their league campaign by beating Kerry in Tralee after all; they have not become a poor side despite what some critics may say.
Sunday might be better seen as an indication of how competitive the football championship has become.
Both of last year's all-Ireland finalists are in the qualifiers already. It will be a difficult road back to Croke Park for the defending champions.
The bright spot for downbeat Tyrone fans may be that it seems utterly implausible so many of their stars will play so poorly again this year.
A team that can bring Darragh Canavan off the bench is a team with serious strength in depth. Tyrone have the resources required to make it back to the All-Ireland the long way round.
Tyrone always play best when they have something to prove, and there is much to prove after Sunday.