Francisco Conceicao proved the hero on his first competitive start for Portugal after his stoppage-time winner snatched a 2-1 victory over Czechia in their Euro 2024 opener.
Cristiano Ronaldo became the first player in the European Championship's 64-year history to appear in six editions, but his landmark moment was overshadowed by a glimpse into Portugal's future.
Conceicao was introduced after 90 minutes and scored just two minutes later, capitalising on a rebound to send Portugal level on points with leaders Turkiye, who beat Georgia 3-1 earlier on Tuesday in Group F.
Robin Hranac's unavoidable own-goal had earlier cancelled out Lukas Provod's rocketed second-half opener before Conceicao announced himself on the international stage at the Leipzig Stadium.
Roberto Martinez's team were the only side to win every qualifying game for this tournament, with a perfect 10 wins from as many matches, and dominated the first half of their opener without reward.
Ronaldo almost marked his landmark appearance with a goal just eight minutes in but rushed an unmarked header in uncharacteristic fashion from Rafael Leao's whipped cross.
Bruno Fernandes angled a deflected long-range effort narrowly over as the one-way traffic persisted, before the Manchester United midfielder's teasing ball just evaded the lunging Leao.
Fernandes was again the architect when his delicate throughball found Ronaldo, who was denied by Jindrich Stanek's fantastic stop from point-blank range.
The Czechia goalkeeper was on hand once more before the interval, parrying away another fizzing Ronaldo strike as these two sides were the first to be goalless at half-time at Euro 2024.
Portugal completed 368 passes in that first-half onslaught, their most on record in a single half at the European Championships since records began in 1980, and little changed after the break.
Ronaldo tested the hands of Stanek with a dipping free-kick just before the hour, though Portugal were stunned soon after when Provod cannoned into the top-left corner from the perimeter of Diogo Costa's area.
Yet a response swiftly followed as Stanek parried Leao's downwards back-post header against Hranac, who could only deflect into his own net to level proceedings.
Diogo Jota had a late finish ruled out by VAR after Ronaldo was adjudged offside before his rebounded finish, though Conceicao pounced from Pedro Neto's left-wing cross to snatch all three points.
Substitute heroics save Ronaldo's landmark appearance
Ronaldo already holds the record for the most appearances in European Championship history (26), though this outing marked another historic moment for the 39-year-old.
Having featured at every Euros since his 2004 debut, Ronaldo is the first to go to six editions of the tournament, where his 14 goals make him the leading scorer in history.
The former Manchester United attacker could not add to his tally here, and it was a familiar tale at the Euros for Ronaldo, who missed the 2016 final victory over France after his gut-wrenching injury.
Eder stepped up as the extra-time hero on that occasion, and he was the last Portugal substitute to score at the Euros before Conceicao did so here.
Conceicao's goal came just 111 seconds after being introduced and marks the fastest such goal since Ferran Torres for Spain against Slovakia in June 2021 (41 seconds) – what an introduction for the Porto man.
Czech need more from Schick
Patrik Schick scored five of Czechia's six goals at Euro 2020, becoming only the second Czech player to be the sole or joint-top scorer at a European Championship tournament – after Milan Baros at the 2004 edition (five goals).
The forward has since lifted the Bundesliga title with Bayer Leverkusen last term, helping Xabi Alonso's side to an unbeaten league season with seven top-flight goals.
Considering his record at the Euros and the 2023-24 trophy-winning campaign, Czechia may want more from their star striker – who was withdrawn on the hour after being cautioned and failing to manage a single shot.
Yet with or without Schick, Czechia could have never prepared for Conceicao's late intervention. Ivan Hasek's side have now lost five straight games against Portugal and must bounce back when they face Georgia on Saturday.