The Nerazzurri netted twice in the closing stages of their previous European home game to defeat Tottenham, but this time Icardi's 87th-minute strike was only enough for a 1-1 draw at San Siro.
The Inter captain was disappointed that his side ran out of time to complete another remarkable turnaround, yet he celebrated a result that looked unlikely when Malcom deservedly put Barca in front just four minutes earlier.
"We played the best team in the world and they scored a typical Barcelona goal," Icardi told Sky Sport Italia . "But we never gave up, we kept fighting and I got the goal.
"We've showed a lot of belief throughout the tournament, as Tottenham scored quite late against us too and we kept fighting then to turn it around. Unfortunately, we just ran out of time here."
Icardi's effort was a scrambled strike from his first sight of goal, but he credited "lucky charm" Matias Vecino for his role as Luciano Spalletti's team maintained their fine form.
"The goal was fortunate; it fell kindly for me and I was able to turn," he added.
"Matias Vecino is our lucky charm, so we keep him on until the end even if he is falling apart. He always gets a goal or an assist."
While the result ensured Barca's progress to the last 16, Inter now face stiff competition from Spurs, who moved to within three points of them.
Spalletti's side travel to Wembley to meet the Premier League club in their next group clash later this month, and Vecino doesn't believe they can go to London in search of a draw.
“We managed to get a point in the last few minutes and now our last two group matches will be key. They passed the ball around really well. They make you run a lot and press excellently.
"I think that we did better in the second half than the first. We can’t head to London now thinking of a draw – that would be a mistake. We will go there to win.
"We are in a position to achieve something important even away to Tottenham.”