The champions trailed 2-0 early in the second half, but following Fabien Lemoine's sending off, Edinson Cavani and a last-minute goal from Matuidi against his former club earned Les Parisiens a 2-2 draw at Stade Geoffroy-Guichard.
Despite having a man advantage for the final 30 minutes of the clash, Matuidi believes that PSG's comeback is a sign of their improvement.
"We did well in holding our own with our strength of character," Matuidi told L'Equipe.
"Last year, we would have lost a game like this, even at 11 against 10. We wanted to continue our unbeaten run, we knew it would be complicated against Saint-Etienne and it was.
"We are happy to have pulled it back to 2-2 and that this run has not stopped today."
PSG host Lorient in their next Ligue 1 match on Friday.