Bruce's job was on a time bomb following the takeover by a super-rich Saudi-led consortium earlier this month from long time owner Mike Ashley.
The Magpies have had a miserable start to the season and are winless after 8 games in the Premier League as they are currently in the relegation zone with just three points.
Saint-Maximin, not being happy with the sacking of Bruce took to his Twitter account to write a heartfelt message to his former manager, thanking the former Manchester United defender for his guidance.
"You are, without a doubt, one of the most gentle people that I have ever met in the world of football. You have been a man of your word, a caring man and a fair man who never hesitated to protect us. I will never forget how you treated me, for that I will be forever grateful.
"You have been a man of your word, a caring man and a fair man who never hesitated to protect us. I will never forget how you treated me, for that I will be forever grateful.
"It has been an honour and a privilege to have you as a coach, thank you Steve."
Newcastle will face Patrick Vieira's Crystal Palace in their next Premier League fixture on Saturday.
