Short of escorting a senior citizen across the street or donating an organ to a relative in need, St-Pierre couldn't have done much more for his good guy image at a public workout Wednesday in advance of UFC 158.
And Diaz, whose matchup with GSP at UFC 137 in 2011 was shelved after failing to show up for news conferences in Toronto and Las Vegas, added to his bad boy reputation.
The California fighter was slated to show between noon and 1 p.m. at the downtown mall that was host to the workout. St-Pierre was due between 1 and 2 p.m.
Diaz never made it. The only glimpse fans got of him was a side shot on a giant promotional poster overhead and a close-up of his sneer on a floor-mounted display.
"We're still trying to find him," said Tom Wright, the UFC's director of Canadian operations.
"Maybe he's on Stockton time," he added, referring to Diaz's home in the Stockton-Lodi area of California.
More likely Diaz time.
Diaz and brother Nate were seen getting on the elevator at the UFC hotel at 2:20 p.m. The St-Pierre entourage arrived at the hotel some 15 minutes later after fulfilling their media obligations at the workout.
"Would of been happy to show for the fans but UFC got me here at 12 last night. George lives here!" Diaz teeted later Wednesday.
Diaz's no-show is hardly likely to trigger anything more than a tongue-lashing from UFC president Dana White given the proximity to Saturday's show at the Bell Centre. Plus Diaz is on the hook to be at Thursday's news conference and Friday's weigh-in.
"He better be at the press conf(erence)," White said in a text to The Canadian Press.
In pulling Diaz from the first GSP fight, White said: "I'd rather pull the fight now than have him not show up the night of the event."
But St-Pierre insisted there's no chance of that this time.
"He's going to show up for sure," said St-Pierre.
The 31-year-old champion, who calls Montreal home, shrugged off Wednesday's mini-drama.
"It doesn't change nothing in my life," he said.
"I don't worry about him. I worry only about myself on that point," he added when pressed on the issue. "I don't care."
Diaz has a history of playing hooky. The UFC says he missed two days filming for a preview show for this card. The Diaz camp says they did not get proper notice.
His camp also complained last month that it had to fly economy to Montreal, using Twitter to campaign for the UFC to upgrade them to business class.
"By train, by horse. I don't care. I want him to come to Montreal. We need to finish the business," St-Pierre said at the time.
In truth, St-Pierre has as little time for the pre-fight public workouts as Diaz does. While other fighters dutifully put on gloves and spar or do light grappling for the watching fans and cameras, St-Pierre doesn't bother.
He argues that he has completed his training camp so why do a fake workout?
Instead he tries to come up with something else to entertain fans. On Wednesday, he pretended to spar with some pint-sized students from a local martial arts academy, Karate Sunfuki. Then he threw signed merchandise into the crowd.
The contrast between the two fighters is exactly why they are facing off in a cage Saturday.
Away from the cage, GSP is Armani. Diaz is hoodie.
Oil and water sells in the UFC.
No. 1 contender Jonny Hendricks was shoved to the side because White said GSP-Diaz was the fight fans wanted to see. St-Pierre agreed.
Both White and St-Pierre have vested interests in giving the fans what they want. The more pay-per-view buys, the better it is for both of them.
The UFC has played up the differences in its marketing of the fight. Promise of a beatdown by GSP and the champion's characterization of Diaz as "most disrespectful human being I've ever met" have seemingly enraged Diaz.
The challenger has objected to such talk, saying he doesn't deserve it. St-Pierre says he hardly remembers saying the words that have become the storyline.
Of course, the 29-year-old Diaz has hardly been lily-white in his pre-fight utterings. After beating B.J. Penn at UFC 137, he accused St-Pierre (23-2) of being scared rather than hurt (the champion eventually had knee reconstruction surgery).
That set off the GSP tirade, dutifully reported by White to the post-fight news conference. And the fight was on.
Then off, then on again.
GSP said later he hadn't understood the rest of what Diaz said when he came over to the fence and tried to speak to him in the stands at UFC 137.
"He said 'homie, something, homie.' His English sometimes is not very articulate," St-Pierre was quoted on the UFC 158 Countdown TV show.
Often Diaz comes across just angry at the world. But the champion has been his target for a long time.
Diaz seems genuinely upset that while St-Pierre is plastered across magazine covers, he is ignored. During a recent media conference call that saw the two fighters go back and forth, St-Pierre suggested Diaz was an "uneducated fool."
Diaz seemed to score when he hit back calling the champion "pampered."
After Diaz was pulled from the first GSP fight, the champion was matched with Carlos Condit. When St-Pierre's knee required surgery, Condit was instead pitted against Diaz at UFC 143 in February 2011.
Condit won, only to be beaten by St-Pierre last November at UFC 154. Diaz was serving his second marijuana suspension after flunking a post-fight drug test following the Condit loss.
Diaz has argued unsuccessfully that he should be allowed to use the drug to help with a social anxiety disorder. But it remains on state athletic commissions' banned list.
Diaz (27-8-1) makes for good copy, with his street lingo and sizable chip on his shoulder. And while he can come across as a boor-like thug, in reality he is an athlete focused on his task with little time for social niceties.
Anyone who includes triathlons in his training regimen is hardly a lightweight.
Diaz simply does not play well with others.
St-Pierre is no stranger to getting abuse from opponents — he says only three didn't trash-talk him — but acknowledged the Diaz show is "getting old."
"But after Saturday it will be over, so I'm happy," he added.