Cristiano Ronaldo was frustrated on his return to international duty as Portugal were held to a 0-0 draw by Ukraine in their opening Euro 2020 qualifier.

Having not featured for Portugal since their defeat to Uruguay at World Cup 2018, Ronaldo was back for Friday's encounter in Lisbon, but failed to inspire a victory as the Euro 2016 champions began their Group B campaign on a flat note.

Andriy Pyatov played a key part in frustrating the hosts, twice denying Ronaldo in the first half before pulling off an exceptional save from Andre Silva.

And Pyatov's heroics paid dividends as Ukraine held firm to secure a hard-fought point, with the onus now on Portugal to respond when they face Group B's other big hitters Serbia on Monday.

Pyatov did well to tip over Pepe's blistering effort, though Ukraine's goalkeeper was fortunate that the offside flag sparred his blushes moments later after his failure to deal with a cross allowed William Carvalho to head in.

Pyatov atoned soon after, twice reacting sharply to keep out successive close-range strikes from Ronaldo and maintain parity heading into the interval.

Ronaldo turned provider with a neat knockdown following the restart, but Andre Silva's resulting effort did not test Pyatov.

The Sevilla forward did better when his next chance came, only for Pyatov to make a superb save at full stretch.

Portugal were almost made to pay for their profligacy with four minutes remaining, but Ruben Dias made a vital block to prevent Junior Moraes clinching the points for Ukraine against the run of play.

Vitaliy Mykolenko risked undoing Ukraine's work in stoppage time when he clumsily bundled into Dyego Sousa, though Portugal's appeals for a penalty fell on deaf ears.

What does it mean? Holders fall flat

The pressure is on Portugal to qualify and defend their title, but with Serbia also in Group B – and Ukraine proving their worth – that task is sure to be a difficult one. Portugal should still have enough, but will need to put in a more clinical display against Serbia next time out, or they could risk falling behind.

Pyatov keeps Portugal at bay

Pyatov was caught out when Carvalho headed in, but with the offside flag coming to his rescue, he made sure to make his good fortune count with two superb saves in a matter of minutes to deny Ronaldo before making an outstanding stop from Andre Silva after the restart.

Neves on the fringes

Wolves playmaker Ruben Neves has impressed in the Premier League this term, but he struggled to stamp his quality on proceedings on Friday, and was replaced just after the hour.

What's next?

Serbia are likely to present the greatest threat to Portugal in Group B, and they are next up for Fernando Santos' side on Monday. Ukraine, meanwhile, face Luxembourg.