Croatia's key players Luka Modric and Mario Mandzukic trained well on Friday and could be ready for at least part of the round of 16 game against Portugal.

Coach Ante Cacic indicated the two men were recovering. "I cannot say if they're fit to play the full match, the whole 90 minutes," he said through a translator on Friday, a day ahead of the game in Lens.

"Everything looks good and but I will decide tomorrow before the match."

Both men, injured during a 2-2 draw against the Czech Republic, looked strong during training on Friday.

Modric, the playmaker, and striker Mandzukic were nursing muscle injuries that forced them out of the final group stage match, a 2-1 victory over double-champion Spain.

Their return is vital for Croatia's chances of progressing further in the tournament at the expense of Portugal and improving on its performances in 1996 and 2008, when it reached the quarterfinals.

The winner of Saturday's match plays Poland or Switzerland in the quarterfinals.

Modric is particularly crucial for Croatia in midfield, helping the team defensively and creating most of Croatia's chances. Croatia collapsed in the game with the Czechs after he was substituted in the 62nd minute.

Mandzukic, the Juventus striker, has scored 24 goals in 67 international games. Croatia lost to Portugal in all their previous three encounters, including a 3-0 defeat in the group stage at Euro 1996, and has failed to score a single goal.

Croatia has been in formidable form in France and advanced to the round of 16 as winner of Group D. But Cacic knows it won't be enough for his players to focus on their game because Portugal will be featuring one of the world's most dangerous strikers after Ronaldo rediscovered his scoring touch with two goals against Hungary.

"We have to defend well against Portugal," Cacic said. "This is a team with great individual qualities. Of course, Ronaldo is their main player. So what we have to do tomorrow is not to allow them to show how strong he is. We have to limit Cristiano Ronaldo."

With Cristiano Ronaldo finally showing his scoring prowess, Portugal is hoping to achieve something it hasn't managed yet at the European Championship - win a match.

After three consecutive draws, Portugal squeezed its way into Saturday's round of 16 game against Croatia, which beat defending champion Spain on Tuesday to extend an unbeaten run to 10 matches.

"Croatia had an amazing game against Spain. We respect Croatia but we also believe we can beat them," Portugal coach Fernando Santos said through an interpreter Friday.

Ronaldo, who netted twice in Wednesday's thrilling 3-3 draw with Hungary, would clearly be the player Portugal turns to for a victory in Lens.

"Portugal is always a team, and Ronaldo is a team player," Santos said. "Without great teams, there are no great players. A great player might decide a single game, but without great team you can't win a tournament."

Against Croatia, the history is on Portugal's side - as it has won all three of their previous encounters without conceding a goal, including a 3-0 victory in the group stage of Euro 1996. More recently, Ronaldo scored the only goal in a friendly win at Geneva three years ago.

"This is a totally different match. I warned my players because we will play a final tomorrow," Santos said. "Croatia has a great team. (Luka) Modric is arguably one of the best players in Europe right now, no one doubts that."

Santos took over from Paulo Bento in October 2014 after Portugal's disappointing showing at the 2014 World Cup and poor start into Euro 2016 qualifying with a 1-0 defeat at home against Albania.

After leading Greece to the knockout stage of Euro 2012 and the 2014 World Cup based on a tightly organized defense, Santos followed the same philosophy and started rebuilding the Portuguese team.

One of the new names was Sporting midfielder Joao Mario, who made his debut as he replaced Ronaldo in Portugal's first match under Santos, a friendly against France at Saint-Denis. Mario has featured in all three matches Portugal played so far at Euro 2016.

"We are aware of what we've done so far. We were very good in some aspects but we need to improve in others," Mario said through an interpreter. "The group stage is behind us now, everything changes. We want to do much better than before."

Mario said "it was not ideal" that Portugal had just three days to rest following its final group match, compared to Croatia's four.

"We know we have not enough time to recover," he said. "But if you get to the knockout stage, you always feel energized."