Portugal arrived in Germany among the contenders to win the tournament for a second time, but despite topping Group F, their performances lowered expectations over how far the Selecao can go.

They scraped a last-gasp 2-1 win over the Czech Republic, impressed in a 3-0 victory against Turkey and then fell to a shock 2-0 defeat by debutants Georgia.

Martinez deployed a 3-5-2 formation against the Czechs and Georgia which his players struggled to get to grasps with, while their more familiar 4-3-3 worked well against Turkey.

After qualifying for the Euros with a 100 percent record, Portugal's form since has been far patchier, with Georgia inflicting the first competitive defeat in Martinez's reign.

Slovenia were the first side to beat Martinez's Portugal in a March friendly, with his 3-5-2 system failing again that day.

But veteran Portugal defender Pepe said that the team needs to step up and follow Martinez's instructions better.

"I think we lost when we should have lost and now we need to learn from that," said the centre-back ahead of the clash with Slovenia in Frankfurt.

"(We must learn) from what we didn't do as players, whether we followed what the coach asked us to do in general, and of course, try not to make mistakes in the next game."

However some in Portuguese media believe the players are puzzled by Martinez's plans and therefore are struggling to execute them.

"We are left wondering whether Roberto Martinez has understood what went wrong against Georgia, and the Czech Republic, for that matter," read a column in newspaper A Bola.

"It's hard to see in the faces of (many players) a team that knows what it is doing, and perhaps more importantly, believes in it."

'We are better prepared'

There are also concerns Martinez is too deferential to 39-year-old striker Cristiano Ronaldo, who did not score in any of the three group games.

Despite rotating virtually his whole team for the defeat by Georgia, Ronaldo still started and Martinez's reasoning did not particularly stand up to scrutiny.

"I think that to continue with the competitive rhythm it's not good to stop and then (have to) reactivate in six days' time," explained the coach ahead of Portugal's capitulation.

Martinez left Belgium after the 2022 World Cup where his team were eliminated in the group stage, scoring just one goal.

In that tournament his selection of Eden Hazard was questioned given his struggles for fitness and form at Real Madrid, with the winger later saying he felt younger players had deserved his spot.

Portugal fans hope the Georgia result will be a wake-up call for Martinez, but the coach claimed his squad was now set up well for the knock-out rounds after sharing around minutes to reserves.

"The focus was on preparing all the players and now we are better prepared for the round of 16," said Martinez.

"We had players on the bench that had to play.

"We don't like losing - it's the first competitive game that we have lost - but the aim was achieved because now we are better prepared."

In Slovenia, Portugal face tricky opponents who reached the knock-outs for the first time in their history by holding England to a draw.

With Atletico Madrid goalkeeper Jan Oblak in goal against his former Real Madrid nemesis Ronaldo and striker Benjamin Sesko on the prowl at the other end, Matjaz Kek's side could prove thorny opposition for a Portugal team struggling to hit their stride.