Ronaldo was largely anonymous in the first half, touching the ball just 12 times - the fewest of any outfield player on the pitch.

IMAGE: Portugal's Nuno Mendes with Goncalo Ramos as he is substituted due to injury. Photograph: Kai Pfaffenbach/Reuters

A major blow for Portugal. Nuno Mendes has gone down with what appears to be a muscular injury and is unable to continue, looking in clear discomfort as he left the field.

Nelson Semedo comes on in his place, weakening Portugal's left side, with João Cancelo expected to shift across to cover. A costly setback in a finely balanced Iberian derby.

Portugal, Spain Goalless in Tense First Half Battle

IMAGE: Spain's Lamine Yamal shoots at goal. Photograph: Hannah Mckay/Reuters

The Portugal-Spain football rivalry, popularly known as The Iberian Derby, is living up to its reputation at AT&T Stadium, with Spain in control but the scoreline still level at the break.

Luis de la Fuente's side dominated possession with 58 per cent, dictating the tempo for long spells through Rodri, as they repeatedly found passing lanes through Portugal's midfield. However, the breakthrough has not arrived, with Mikel Oyarzabal wasting a clear early chance and Portugal's defence holding firm under pressure.

Cristiano Ronaldo has offered little defensive contribution, leaving Bruno Fernandes and Portugal's midfield trio to shoulder much of the pressing responsibility, as Spain continued to probe and stretch the lines.

Portugal threatened in brief moments, most notably when João Félix sparked chaos inside the Spanish box, while Nico Mendes came closest with a deflected effort that struck the crossbar late in the half.

Despite Spain's dominance in territory and control, the game remains finely poised heading into the second half of this intense Iberian Derby.

IMAGE: Portugal's Diogo Costa saves a shot by Spain's Alex Baena. Photograph: Omar Aziz/Reuters

Spain have made the brighter start in their FIFA World Cup Round of 16 clash, forcing Portugal goalkeeper Diogo Costa into a couple of outstanding saves to keep the scores level after 25 minutes.

The European champions have looked sharp in possession, carving Portugal open with some slick passing moves.

Mikel Oyarzabal had Spain's first big opportunity but failed to make clean contact after a beautifully worked attack. Moments later, Lamine Yamal was played through with an excellent pass, only for Costa to produce two brilliant saves during a dangerous Spanish counter-attack.

Portugal were exposed after Nuno Mendes was caught out of position, allowing Yamal space to drive into the final third. Despite Spain's early dominance, Portugal have held firm, with Costa proving the difference in a tense and entertaining Iberian derby.

IMAGE: Spain's Pedri in action with Portugal's Cristiano Ronaldo. Photograph: Maria Lysaker/Reuters

Portugal and Spain are locked at 0-0 in a tightly contested first half of their FIFA World Cup Round of 16 clash, with a place in the quarterfinals on the line.

Cristiano Ronaldo is fighting to keep his World Cup dream alive, while Spain are looking to continue their bid for another major international title.

IMAGE: Spain's Marc Cucurella and teammates during training. Photograph: Kai Pfaffenbach/Reuters

Key Points

• Spain maintains an unchanged lineup for their World Cup round of 16 match against Portugal.
• Portugal makes one strategic change, with Joao Felix replacing Rafael Leao in the starting XI.
• Cristiano Ronaldo captains the Portuguese side, following his announcement of international retirement post-tournament.
• Key players like Pedro Porro, Dani Olmo, Ruben Dias, and Bruno Fernandes are confirmed starters for their respective nations.

Spain named an unchanged side for Monday's World Cup round of 16 match against Portugal, while Roberto Martinez made one change by bringing in Joao Felix for Rafael Leao in attack.

Luis de la Fuente keeps faith with the Spain team who beat Austria in the round of 32.

Pedro Porro remains at right back, with Dani Olmo in the playmaker role.

Portugal's Strategic Team Selection

IMAGE: Portugal's Pedro Neto, Ruben Neves, Matheus Nunes, Samu Costa and Jose Sa on the pitch before the match. Photograph: Maria Lysaker/Reuters

Joao Felix starts alongside Cristiano Ronaldo and Pedro Neto, with Leao on the bench.

Ronaldo captains Portugal after saying he will retire from international duty after the tournament.

Lineups:

Portugal: Diogo Costa; Joao Cancelo, Ruben Dias, Renato Veiga, Nuno Mendes; Vitinha, Joao Neves, Bruno Fernandes; Pedro Neto, Joao Felix, Cristiano Ronaldo.

Spain: Unai Simon; Pedro Porro, Pau Cubarsi, Aymeric Laporte, Marc Cucurella; Rodri, Pedri, Dani Olmo; Lamine Yamal, Alex Baena; Mikel Oyarzabal.