"A finisher, that's always been my strong suit," the 22-year-old Wiedeman had said by way of introduction prior to his home debut in Toronto. "So if I get a half-chance I'm looking to take it and tuck it away."
Wiedeman did just that, scoring in the 67th minute to give Toronto a 2-1 win over the slumping Colorado Rapids before 18,225 at BMO Field.
It was his first MLS goal in his 10th career game — and his second as a substitute since coming to Toronto in the deal that sent midfielder Julian de Guzman to FC Dallas last Friday.
"Definitely a poacher's goal," Wiedeman said afterwards with a smile.
Coming in on the back of victories over New England and Vancouver, Toronto (5-11-4) is now riding its first three-game win streak since April 2008.
Colorado (7-12-1) has lost four straight and six of the last seven, with all six defeats coming by one goal. It also marked the fourth time this season the Rapids have lost after opening the scoring, second only to Montreal (five).
Fullback Doneil Henry helped make the go-ahead goal. Beating a defender in the corner, he sent the ball towards the box and, after rookie Luis Silva swept it towards goal, Wiedeman poked it in.
"He just has an eye for a goal," said Mariner, a former England international who knows a thing or two about scoring. "I saw it in training last week in New England. When he was shooting on goal, that kid didn't miss."
Added Mariner: "I've been told he's probably one of the best finishers in MLS. But he's been behind some very very good players in Dallas."
It was a game of woeful defending by the Rapids and Mariner admitted lambasting his team at halftime for failing to take advantage.
Amazingly Colorado went to the dressing room up 1-0 on the strength of a Conor Casey goal in the 23rd minute, despite being repeatedly carved open in defence.
"I gave them both barrels at halftime," said Mariner. "I think we could have been a couple of goals up after 10 minutes .... I just said to the lads 'Who was that who was playing in red tonight?' Because I didn't recognize them. And there was a bit of a stunned silence, but they know. They know when they're playing well, they know when they're not playing well. And they didn't. You can't play well in this league for 10 or 15 minutes and expect to get results. You can't.
"We gathered the troops, went out with a slightly different formula and I thought the second half was terrific."
Jamaican international Ryan Johnson, making up for a flubbed penalty in the third minute, replied for Toronto in the 51st.
Amidst the celebration of the win was the fact that a game that should have been decided early in the first half was still in the balance until the final seconds. But with 19 points, Toronto is no longer all alone at the bottom of the league and is now just nine points out of the fifth and final playoff spot in the East.
There is more work to be done, however.
TFC's current lack of depth was illustrated by Wednesday's bench, which featured four teenagers: goalie Quillan Roberts (17), midfielders Oscar Cordon and Matt Stinson (both 19) and forward Keith Makubuya (19). The 'greybeards' on the bench were 21-year-old defender Aaron Maund, the 22-year-old Wiedeman and 25-year-old defender Dicoy Williams.
"It shows you where we are at the moment," Mariner said of the green substitutes. "Earl (director of team and player operations Earl Cochrane) and I are working extremely hard behind the scenes to get some people in. (We) may have an announcement (Thursday)."
Toronto's record under Mariner is 4-2-4 — after a 1-9 start under former manager Aron Winter — despite playing those 10 games in 32 days, with six of those contests on the road.
"A ridiculous run of games," said Mariner. "And basically playing with the same players, who were playing hurt. Some of those guys don't want to be taken out of the team."
The contest was the first for Toronto since leading scorer Danny Koevermans tore knee ligaments in Saturday's 1-0 win in New England. The designated player is not expected to be back until next May.
Mariner moved Silva up front with Johnson. Eric Avila returned to the lineup in midfield.
There was redemption in the second half for both Henry, victimized on the Colorado goal and told as much by Mariner in a rare moment of locker-room finger-pointing, and Johnson, who rattled a third-minute penalty off the post.
Captain Torsten Frings is the team's designated penalty-taker but he missed his last attempt and Johnson asked to take it, saying he felt confident.
"Basically a captain's decision," said Mariner.
Frings said later he doesn't like a lot of chit-chat on the pitch, so when Johnson stepped up, he stepped aside.
Casey put the visitors ahead after some nice give-and-go off a Rapids throw-in. Hunter Freeman floated in a cross and the powerful Casey outmuscled Henry before sending a looping header past Milos Kocic. It was the 50th MLS career goal for Casey, who appeared in two games for Toronto in 2007 before moving to Colorado.
"Poor marking in the box," said Mariner. "Great header by Conor, fantastic header."
Kocic kept Toronto in the game with a splendid foot save off Wells Thompson in the 50th minute.
A minute later Johnson pulled Toronto even after Silva found him with a short pass following some woeful Colorado defending. Johnson calmly angled the ball past Matt Pickens for his fourth goal of the season.
"A beautiful little flick over their defender and then a really nice little tap-in to finish it off, was a quality goal," Mariner said admiringly.
"He's a great kid, He wants this club to be successful and he's going to drag this club along with it." he added.
Colorado has now lost six career games to Toronto at BMO Field, although it defeated FC Dallas in Toronto to win the 2010 MLS Cup.
Toronto's next league match is July 28 against visiting Houston. Next up is a friendly Saturday against England's Liverpool at Rogers Centre.
"If I'm brutally honest, it couldn't have come at a worse time," Mariner said of the Liverpool game. "Because I do have some sore young men in there ... but it's Liverpool, you know."
The ex-Arsenal and Ipswich man said he will probably have to dig deep into his roster to field a lineup.
"It's a great honour to play against them and we'll want to try to give a good account of ourselves, but we have to be cognizant of the Houston game which is coming up quick."