Mariner, a former English international forward, called the young California striker intriguing, young and "very very hungry."
Then he delivered a doozie.
"He's one of the best finishers I've ever seen in the modern era," Mariner said. "I'm looking for him to really take the bull by the horns and take this opportunity."
Nine months later, Wiedeman is a valued squad member of the MLS team. But he is not Robin Van Persie.
Today, he laughs about the comment that still follows him.
"I didn't even realize it at first and then my agent sent the article to me just kind of ribbing me, giving me hell for it," he recalled. "Because that's a pretty big thing to say.
"Obviously you want your manager to have confidence in you," he said, before pausing with a small laugh, as if not sure where to go next.
Even today, he'll post something on Twitter and hear back "best tweet of the modern era."
"It's good little ribbing," he said good-naturedly.
Mariner may have been looking to put the best face on a trade that was essentially an attempt to shed Toronto of designated player Julian de Guzman's salary.
Toronto (1-2-1) hosts red-hot FC Dallas (4-1-0) on Saturday. It's the best start in Dallas franchise history, and the club was tied with Montreal for the most points (12) in the league going into this week's play.
Dallas has done it in spite of a 13-player turnover since December that include the acquisition of striker Eric Hassli from Toronto. The big Frenchman has been restricted to 36 minutes of play in three appearances as a substitute.
Wiedeman scored twice in 15 appearances last season under Mariner with his second score — against Colorado — helping Toronto to the last league win of its dismal 5-21-8 season.
With a new management regime in place this year, he has yet to make it off the Toronto FC bench. But the 23-year-old isn't complaining. Far from it.
Wiedeman normally has a smile on his face, with a warm greeting for reporters as he walks past them to practice each day.
"I have the best job in the world right so how could I not be (happy)," he said. "I'm so much more fortunate than a lot of other people.
"Obviously I want to be playing but I love my job and it will come eventually. So not point in being down, that's not going to help anything. ... I'm living the dream, right? Getting paid to play a sport."
His attitude has not gone unnoticed.
"Weeds has been absolutely fantastic," said manager Ryan Nelsen. "He's not complained one bit. None of the players have complained.
"Nowhere near from what I've been used to in England," he added with a smile. "We were shocking, we used to moan all the time. These guys are brilliant. And Weeds is right there. He never complains. I've put him in several positions. He goes about his business very well.
"For me he's improving and getting better and better and better. I love the guy. I love him round the locker-room. He's a great example for the younger guys and I guarantee when he gets his chance, because he trains like this, he will take it."
Nelsen made his comments after a training session in which Wiedeman hammered a long-range shot off the crossbar.
Knowing Nelsen, Wiedeman may get some time off the bench Saturday if the time is right. The young striker was drafted by FC Dallas in the second round, 21st overall, in 2010 before being traded to Toronto in the deal that shipped de Guzman to Texas last July.
De Guzman has since moved to a second-tier team in Germany.
Wiedeman made seven starts for Toronto last season. He only had one start and eight appearances in three seasons in Dallas, which briefly attempted to turn him into a right back.
He made progress in Dallas but it was slow. He didn't dress in his rookie year, dressed for a few games in his sophomore season before seeing more regular action in his third season, which was interrupted by a sports hernia operation, before being traded.
Wiedeman is well-liked by his fellow players in Toronto. Midfielder Jeremy Hall played against him in college and got to know him first during a trip by Generation Adidas players to Madrid.
As a Generation Adidas player, Wiedeman's salary did not count against the Toronto cap. The program is a joint venture between MLS and U.S. Soccer designed to help promote young soccer talent in the U.S.
Then Hall got traded to Dallas, where the two often hung out. Wiedeman rejoined Hall in Toronto last season, living several floors above him in the same building so the two would commute together to work.
In Orlando during pre-season this winter, Hall roomed with fullback Richard Eckersley while Wiedeman shared with defender Logan Emory in the adjoining room. The door was rarely closed as the four got along famously.
And Wiedeman stayed with Hall earlier this season until he found a new place.
"He's a great player, he's always working hard," said Hall. "Very friendly, social person off the field. Easy to talk to.
"That's great to have on your team. Because obviously everybody wants to play and it's hard, especially with new coach, new players that they're bringing in — experienced players at his position as well so it's tough to get in there.
"But he's doing well in training ... I hope he gets a shot."
Toronto has been starting Robert Earnshaw as the lone striker, with Hogan Ephraim playing just off him. Reggie Lambe and John Bostock have been given the role of attacking wingers.
Wiedeman and fellow forward Justin Braun have been biding their time.
All Wiedeman can do is train hard and be prepared.
"You're not playing but you have to be mentally tuned in, you have to be physically ready ... If that opportunity comes and you're not, then that opportunity's probably not going to come knocking again," he said.
"So I'm just trying to make sure that I'm tuned in, my body's right, fitness is right, mentally I'm right, ready to go as soon as they need me. It's a long season. I'm sure I'll be on the field at some point."
The roster situation is only going to get more complicated, however, with Argentine striker Maximiliano Urruti expected to arrive later this month and Dutch sniper Danny Koevermans expected back in June after a prolonged injury layoff.
But Wiedeman is savouring every moment, especially under the new regime.
"I love it, actually, everything about it. There's a buzz around the locker-room, for sure ... When we put it all together on the field here, it'll be the best place to play in MLS," he said.
"Ryan and the staff are very clear about what they want. And it makes things simple for us," he added.
Wiedeman made US$123,000 last season, the last year of his Generation Adidas deal, to rank 11th on the TFC books.
The club and Wiedeman's agent agreed on a new deal in the off-season, a process the player says helped remind him of the realities of MLS soccer.
His contract remains guaranteed but others are not so fortunate.
"I was very happy when I finally put pen to paper," he said.
Wiedeman tried to leave nothing to chance, taking only a handful of days off after the season ended before continuing his workout regiment.
As he bides his time, he thinks of U.S. international Herculez Gomez, who bounced through MLS before finding his niche in the rarefied air of Mexican soccer.
"I'm not saying I'm going to be the next Herculez Gomez. But you work and you wait for an opportunity," he said. "That's all you can do."