When Cristiano Ronaldo failed to deliver, it fell to an 18-year-old newcomer starting his first game to help Portugal reach the semifinals of the European Championship.

Teenager Renato Sanches had a coming-of-age outing for Portugal, scoring with a stunning shot from distance to cancel out Robert Lewandowski's early goal for Poland, and then converting his penalty in Thursday's shootout.

At 18 years and 316 days old, Sanches became the youngest player to score in a knockout round at the continental competition, quite a way to return the trust placed in him by coach Fernando Santos on his first start of the tournament.

"Things weren't going our way and I called Renato to change something. and we were lucky enough to have him score," Santos said. "He played a great game. He is still growing and has a lot to offer. He will be a better player in the future."

Ronaldo's teammates then searched him out in the second half, while their captain let them down with a series of misses.

Ricardo Quaresma had to seal a victory again after coming off the bench, stepping up to score the decisive penalty in the shootout following Rui Patricio's outstanding save to deny Jakub Blaszczykowski. Five days earlier, Quaresma had scored in extra time to give Portugal a 1-0 win over Croatia in the last 16.

However, he would never have had to be the team's savior a second time if Ronaldo had shown his usual ruthlessness in front of goal.

Ronaldo appeared to get rattled after the Real Madrid forward fired Nani's pass into the side netting, giving Poland's supporters a chance to mock with him chants about his Spanish league rival, Lionel Messi.

And it only got worse when he failed to connect with three passes that teammates set up for him in scoring positions during the latter stages of the match.

Despite the missed chances, Santos strongly defended Ronaldo's performance.

"Cristiano played an amazing game," Santos said. "People always focus on Cristiano because he has to score, but he has been playing amazing football."

More likely, it was the latest instalment in his up-and-down time at Euro 2016.

Ronaldo has reached three milestones in France. He surpassed Luis Figo's record of 127 appearances to become Portugal's most capped player, set a record for final appearances with 19, and became the only player to ever score in four different editions of the tournament.

But the three-time world player of the year has also lost his composure at times, both on and off the pitch, and his two strikes against Hungary are his only goals in five matches so far.

All eyes now will be on his next chance to redeem himself, against either Belgium or Wales in Lyon on July 6.