Mathieu, Andre de Grasse of Canada and Danny Talbot of England were the leading runners among 24 to advance to Thursday's semifinals, ahead of the final that evening.
The Bahamian timed 20.55, well outside the world record of 19.19 held by Usain Bolt, who still showed off his speed on Wednesday when he was quick to deny making disparaging remarks about his experience in Glasgow.
Bolt tweeted on Wednesday that "I'm waking up to this nonsense" and called the report "lies."
Bolt spent Tuesday mixing with Prince William, his wife Kate, and Prince Harry. On Wednesday, he watched the Jamaica netball team lose to New Zealand, and was blocked by his manager from the media, saying only "awesome" to questions about his opinion of the games.
Following a left foot injury, the world's fastest man is competing only for Jamaica's 4x100-meter relay on the weekend. (Wrestling: Bajrang Gets Silver | Lalita Misses Out Gold | Satyawart Settles for Silver)
Elsewhere at the games on Wednesday:
DIVING GOLD: The Canadian team of Meaghan Benfeito and Roseline Filion won gold in the women's synchronized 10-meter platform, the first diving event at the Royal Commonwealth Pool in Edinburgh.
NO HEADGUARDS CRITICIZED: Australian Daniel Lewis was ruled out of the welterweight quarterfinal after failing a medical check, and he called for headguards to be restored for amateur fighters. Lewis had a badly cut eye after beating Kehinde Ademuyiwa of Nigeria on Monday. Lewis did not recover sufficiently in time to meet Mandeep Jangra of India in his next bout, so Jangra was given a walkover. Lewis criticized a move last year to remove headguards from amateur male fighters, with experts suggesting they contributed to concussions. "For all these people debating about headgear for amateurs, bring the headgear back 100 percent," Lewis said. "When you have to fight five times in a week this ... ruins people's dreams." (Boxer Mandeep Jangra Advances to 69kg Semifinals | Pinki Rani, L Sarita Devi Reach Boxing Semis)
NO GOALS: Wales and Malaysia both failed to score any goals in their field hockey matches at the games. Not surprisingly, they played to a scoreless draw in their final match against each other and didn't score in any of their previous three group games. It was also the first time in Commonwealth Games history that a group game had ended without either team scoring.
ENGLAND FIRST: In gymnastics, Max Whitlock of England won gold in the men's all-around individual gymnastics final with a score of 90.631 points. Daniel Keatings of Scotland took the silver and Nile Wilson of England earned the bronze.