Andriy Shevchenko felt the years fall away as he fired co-hosts Ukraine to a 2-1 victory over Sweden in Kiev.
The former Chelsea and AC Milan striker, 35, produced two high-quality goals in the second half after Zlatan Ibrahimovic had given Sweden a 53rd-minute lead. The result places Ukraine, making their debut in the tournament, at the top of Group D and gives them a great chance of qualifying for the quarter-finals.
"I feel that I'm 10 years younger today," said Shevchenko, who rejoined Dynamo Kiev in 2009. "I want to say thank you to everyone who has worked with me over the past six months."
He added: "I couldn't imagine that I'd be able to play because I had lots of problems with my knee and back. Lots of people gave me support and I must thank them because I'm in good condition today.
"It was probably one of the best games I've played in the last seven or eight months. It's a great day for Ukraine. We should go through this group, but we expect two more very tough games (against France and England)."
Ukraine coach Oleg Blokhin was unimpressed by Sweden's tactics and perceived lack of sportsmanship.
"The Swedish team only played for a draw and looked only for counters through Ibrahimovic," Blokhin said. "Also they weren't very fair because when our player was lying on the pitch and the referee should have stopped the game, they had a chance and scored. I really don't like it."
Sweden coach Erik Hamren branded his side "cowards" following their defeat at the Olympic Stadium.
"We're not reaching the level we want to and that's my responsibility as a coach," he said. "We didn't show the courage we were supposed to. Only five or six players did. We all need all the players doing that.
"We were cowards in the first half and should have done more. I'm not happy with the team, I was expecting more. The players do want it very much, but we should have scored with the three last chances we had."