On Tuesday, Pato celebrated his first Champions League start of the season by heading Milan's equaliser in a 1-1 draw with Malaga, keeping their Group C destiny in their own hands.
It was his first goal since an Italian Cup match against Novara in January.
The 23-year-old has suffered an extraordinary 15 muscular injuries in the last two years, costing him, among other things, a place in Brazil's squad at the 2010 World Cup.
This season appeared made for Pato to finally make his mark after Milan offloaded their two main strikers from last term, Zlatan Ibrahimovic and Antonio Cassano.
His two goals for Brazil against Sweden in August also suggested he was ready to establish himself finally.
Instead, he suffered yet another injury in August, this time to his thigh, and allowed Stephan El Shaarawy to flourish in his place.
"I just need to play. I want to help my team-mates and always try to do the best," he said after Tuedsay's match.
"What do I want to say after a difficult year? Just that I'm not worried, I have always worked hard."
Milan will now be crossing their fingers and hoping that Pato's injury nightmare really is over.
STUNNING DEBUT
When they signed him as a 17-year-old from Brazil's Internacional, Milan believed they had uncovered one of the country's great prospects.
Pato had made a stunning professional debut with Internacional in Brazil in 2006, scoring within a minute of his first appearance and setting up two goals in a 4-1 win over Palmeiras.
The same year he became the youngest player to score in a FIFA-organised competition when he hit the target for Internacional against Al-Ahly in the Club World Cup at 17 years, 102 days.
He played only a handful of games for Internacional, who had deliberately kept quiet about him, before being snapped up by Milan. He also scored on his debut for Brazil against Sweden in 2008.
But the expectations proved too high, and his career was not helped by a high-profile marriage to Brazilian soap opera actress Sthefany Brito which lasted less than a year.
He was already struggling to impress Brazil coach Dunga when an injury ended his hopes of making the 2010 squad.
Last season, in addition to injuries, he failed to develop much of an understanding with volatile striker Zlatan Ibrahimovic, who seemed to prefer the company of Antonio Cassano in attack.
He came within a hair's breadth of leaving the club in the January transfer window, but decided to stay on.
Still only 23 and a regular member of the Brazil squad when he is fit, Pato could yet live up to his early billing if he can have an injury-free run.
"When you suffer one injury after another, it is to be expected that if affects you mentally," said coach Massimiliano Allegri.
"For him, just the fact that he is on the pitch is a weight off his shoulders. Once he regains confidence, he will start scoring."
