Ronaldo was cup-tied for the Champions League last season after signing from Real Madrid in January but once he shakes off a hamstring problem he will be raring to go this term having shed a lot of weight.
"It will be a surprise for everyone. He seems like a model. He will have a great season, he is very motivated and really wants to demonstrate again that he is the strongest attacker in the world," said Milan coach Carlo Ancelotti.
Emerson has arrived after being eased out at Real but he faces a battle to break into Milan's midfield with Gennaro Gattuso, Andrea Pirlo and Clarence Seedorf key factors in their seventh European Cup triumph last season.
Massimo Ambrosini, the most likely midfielder to make way, has made an excellent start to the league season and will prove difficult to budge.
The third signing was 18-year-old forward Pato from Internacional. He is ineligible until January but much is expected after his performances for Brazil in the Under-20 World Cup.
Milan's best bit of business was keeping playmaker Kaka despite numerous bids from Real. The 25-year-old was instrumental in the Champions League victory last term, especially in the semi-final win over Manchester United and looks set to light up the competition again.
Defender Paolo Maldini, 39, resisted the temptation to quit after the 2-1 win over Liverpool in Athens in May and is targeting a ninth European Cup final and a sixth winner's medal before he finally retires after an astonishing career.
Knee surgery will keep him out until late September though and with other ageing defenders Cafu and Serginho, Milan's back line looks their weakest point.
