Lewandowski drew a blank for the fourth match in succession at this European Championship as Poland advanced to the quarter-finals courtesy of a 5-4 penalty-shootout victory over Switzerland.
Adam Nawalka's team gave up the lead to draw 1-1 in Saint-Etienne, where their skipper started strongly but faded physically as the contest wore on.
Questioned after the tight affair on whether or not there are concerns within the squad over the Bayern Munich striker's drought, Fabianski said: "No, we're not worried at all.
"We're quite happy with where we are at the moment [as a team]."
"That would complete him, probably," he said. "You've got to say that Robert does his job as well. Even though he's not scoring goals he gives a lot to the team.
"Even in the first minute of the game, we created something from his pressure, that put them under a stressful situation.
"That's what he gives us, even though we're not creating as much as we would like to for him. He's still trying to do his best for the team."
Fabianski has benefited from an injury to his former Arsenal colleague Wojciech Szczesny to start the last three games of the tournament and the Swansea City shot-stopper was in a philosophical mood regarding his elevation from the bench.
"It's the life of a goalkeeper," he said. "It's always been like that, especially in the national team. You can never really please everyone.
"There's always going to be one, not disappointed, but a little bit frustrated. Obviously we are playing regularly with our clubs."
Of Portugal's struggle to reach the knockout stages, he said: "They were in a tough group.
"You can see with the changes UEFA made with three teams [from some groups] going through to the next round, it made it more adventurous for the so-called smaller teams.
"We're trying to do our best and make Poland proud."