"It was a very exciting moment for me and it means I have remained ready throughout," said the striker after Milan's 1-0 win at the Stadio Friuli.
He had been roundly criticised for his recent performances and dropped in favour of Alexandre Pato, but came off the bench to secure a stoppage-time strike.
"There wasn't long to go, but I came on and guaranteed the game three very important points to climb back up the table.
"I have never abandoned Milan and over the years I've been here I have scored a few crucial goals. All I can do is give 100 per cent."
Milan coach Carlo Ancelotti added: "We start again from a great Gilardino introduction, as he scored a decisive goal in a crucial match. He made the most of the moment, but had never been shelved. There is merely more competition in the team.
"He has certainly 'suffered' the return to fitness of Ronaldo and Pato's arrival, but he will have his space. The Coach has to make decisions and in the final minutes Gilardino was more suited to a long ball than Ronaldo."