Cristiano Ronaldo is the world's best player and is always hungry for more, Portugal team-mate Mario Rui said.
Ronaldo inspired Portugal to a 6-0 thrashing of Lithuania in Euro 2020 qualifying on Thursday, scoring a hat-trick in the Group B win.
Mario Rui lauded his 34-year-old team-mate after Portugal moved a step closer to qualifying for next year's showpiece tournament.
"He is the best in the world, never tired of winning, wanting more, and it is this hunger that makes him what he is," the Napoli left-back said, via A Bola.
"We are happy to have him on the team and I hope he will continue to give us joy as he has done so far."
Pizzi, Goncalo Paciencia and Bernardo Silva also scored for Portugal, who are second in the group on 14 points, behind Ukraine (19) but ahead of Serbia (13).
Portugal can secure their place when they visit Luxembourg on Sunday and Mario Rui said a tough task awaited his side.
"Mathematically, we know it is not [guaranteed] yet," he said. "We will face a tough team, Luxembourg, we still had that confirmation with the result in Serbia [who won 3-2].
"We know it will be a very difficult game, but our goal is to be at Euro 2020 and we will try to bring all three points to Portugal."