With Portugal qualified for the last-16, Martinez began with only three of the players that started the victory over Turkey, including Cristiano Ronaldo.

But if Martinez hoped a few players would push themselves into contention for the knockout round clash with Slovenia, he was left disappointed as Portugal were outplayed.

"It's a defeat. We started with low intensity, we conceded early and that's what Georgia needed," Martinez told reporters.

"We weren't clear-headed enough with the last pass and in front of goal, and their goalkeeper had an amazing performance. We tried to score but couldn't and that made Georgia believe all the more. They deserved to win.

"Today was the day to give other players an opportunity, players that we needed to see how they were doing, players with their own worth. Today I didn't want to put on Ruben Dias, Bernardo (Silva) or Bruno Fernandes."

Tens of thousands of raucous Georgia fans roared their side, ranked 74th in the world, to victory over the 2016 champions on what proved a frustrating night for Ronaldo.

He failed to score in the group stage of a major international tournament for the first time in his career, having registered in the previous 10 he had appeared in, dating back to Euro 2004.

Although the shock defeat stung, Martinez said it could work as a wake-up call.

"We didn't underestimate Georgia, but Georgia were playing the game of their history," he said. "And we were playing the last game when we were already top of the group.

"It was difficult for us to match the same intensity. Losing today will prepare our team better from a mental standpoint.

"I changed seven or eight players from the last game and I wanted all the players to be as well prepared as possible for the knockout stages."

Martinez was full of praise for Georgia.

"They showed an incredible belief," he said. "I'm sure that scoring early helps, but probably the biggest surprise was that they were able to maintain the level of belief and intensity for 90 minutes.

"I think the coach has done an incredible job and they deserve the credit today."