The goalless draw, played out in wretched conditions, may pass quickly into the memory.
But for Gallas it was a more than worthwhile learning experience for the likes of Abou Diaby, Lassana Diarra, Alex Song, Denilson, Theo Walcott and Nicklas Bendtner.
"I told them before the game to be careful, because it would be a difficult match, and to be ready for the fight. They did the job very well," the Arsenal skipper said.
"The young guys are ready and have shown their character."
Gallas added: "I was not surprised by their quality. Before the season started I knew the players would be ready for the big fight and try to be on the top.
"What is good is that everybody can play and can show how they are strong."
The France defender added: "We are very happy, but it is not finished yet as we have two more games to play in the Champions League.
"Now we can rest a little bit and think about the Premier League.
"We have to be ready for the big fight again when we play Sevilla because they lost to us and will now want to beat us in their stadium."