DONETSK, Ukraine: After a mixed first season with Real Madrid, Fabio Coentrao has enjoyed a renaissance with Portugal at Euro 2012, despite the onerous task of having to provide cover for Cristiano Ronaldo.

Although he sustained a knock to his left leg that ruled him out of training on Saturday, the former Benfica player is expected to line up in his side's semi-final against Spain in Donetsk on Wednesday.

Portugal coach, Paulo Bento, would hate to lose the services of such an indispensable player.

Bento is not prone to squad rotation, but the fact that Coentrao has started, and finished all four of Portugal's matches so far, demonstrates the left-back's strategic importance to the team's approach.

A former left-winger, Coentrao is an accomplished dribbler and attacking player, but his role for Portugal is clearly defined; secure the left flank to give Ronaldo a solid platform upon which to perform.

The opening 1-0 loss to Germany raised doubts about Portugal's resolve, but Bento's men quickly got back on track by beating Denmark 3-2, with Coentrao instrumental in setting up Silvestre Varela's 87th-minute winner.

In the wins over the Netherlands and the Czech Republic that followed, Coentrao continued to alternate between covering Ronaldo's attacking forays, and charging forward to overload the right side of the opposition defence.

However, faced with Spain's armada of attacking talents, he will have to rein in his attacking instincts.

Coentrao is likely to come up against Madrid team-mates Xabi Alonso, Sergio Ramos, Alvaro Arbeloa and Iker Casillas, but his primary concern will be Spain's David Silva, whose intelligent probing always requires close attention.

Having struggled to displace Marcelo in the Real Madrid first team, Coentrao is using the Euro to remind Coach Jose Mourinho of his worth.

A close-season acquisition from Benfica in 2011, Coentrao flitted between roles in midfield and defence in his debut Madrid campaign, labouring to justify his 30 million euros ($37.4m) price-tag.

He was notably the subject of strong criticism after Madrid's 2-1 loss to Bayern Munich in April in the away leg of their Champions League semi-final defeat.

A month earlier, he had been caught out by paparazzi with a cigarette hanging from his mouth after a night out to celebrate his 24th birthday.

Unimpressed, Mourinho promptly dropped him.

From the player's perspective, Coentrao says the gulf between his performances for his club and his national side is a question of “confidence”.

“The environment is completely different,” he said.

“With my team-mates' confidence, I'm able to show what I'm capable of.”

Ronaldo, for one, needs no reminding of Coentrao's worth.