Cristiano Ronaldo will be placed in quarantine for two weeks after the Juventus star returned to Turin.
The Portuguese attacker spent almost two months in his native Madeira as the coronavirus pandemic struck Italy, forcing the country into lockdown.
Ronaldo was expected back on May 18, when clubs were initially scheduled to return to training.
The Italian government moved that date forward to May 4 after many regions gave permission for training centres to open again, prompting Juventus to recall the foreign players who had left the country as the Covid-19 situation grew worse.
The players coming back will have to undergo two weeks of quarantine upon their arrival in Italy before they can begin training again.
While Ronaldo, 35, and his family were on the way back to Turin, many of his team-mates were being tested for coronavirus at the Juventus Training Centre.
Aaron Ramsey, Federico Bernardeschi, Juan Cuadrado, Carlo Pinsoglio and Merih Demiral, who is recovering from injury, were all examined.
As of Tuesday, training will resume but players will have to work on their own to abide by social distancing rules.