Poland boss Adam Nawalka singled out Robert Lewandowski for praise despite another goalless showing at Euro 2016, describing the Bayern Munich striker as the team's "steam-powered locomotive".

Lewandowski looked bereft of confidence at the Stade Velodrome as Poland eased through to the last 16 thanks to a 1-0 defeat of Ukraine, Jakub Blaszczykowski scoring the only goal nine minutes after his introduction at half time.

Blaszczykowski's immediate impact was in stark contrast to Lewandowski's troubles.

The former Borussia Dortmund star, who missed a fourth-minute sitter, has now failed to score in six international appearances and appears to be mired in a poor run of form at just the wrong time.

Nawalka dismissed any concerns, though, and praised his number nine's all-round display.

"The fact Robert Lewandowski hasn’t scored a goal yet is not a problem whatsoever for our team," he said.

"Robert is doing a lot of fantastic work, he has a great influence on our team and the way we play. He's incredibly important for us, he’s like the steam-powered locomotive of the team.

"He's a player that helps us. He plays in a supportive role in every possible way and sacrifices himself for the team.

"The fact he hasn’t scored yet doesn't matter, it's just a matter of time. He's creating more chances and I think he will score in the next match."

Saturday's victory was far from straightforward with Ukraine playing with the attacking abandon of a team already eliminated following back-to-back defeats at the hands of Germany and Northern Ireland.

"We're very happy with the win," added Nawalka. "That's another three points, seven in total. It's a very good result, we haven't conceded a goal and we are still going forward.

"We knew Ukraine would be a difficult rival, they play good football and that was proven on the pitch.

"We started well and created chances but we lost control of the midfield and stopped winning the second balls. This also explains the substitution at half-time [bringing on Blaszczykowski]. We were losing control of the midfield and I wanted to reinforce that area."

After finishing second in Group C behind Germany, Poland now go to Saint-Etienne to meet Switzerland on Saturday, a match Nawalka confirmed Blaszczykowski will start.

"Switzerland are a team that plays at a high level," he said. "They are one of the more interesting teams at the tournament and we are expecting a difficult game but we have faith and optimism that we will go further.

"The fact that Switzerland will have two extra days to rest doesn't make any difference for us, we are very well prepared physically and my players will have enough rest."