The substitute’s first-ever goal in Europe’s leading club competition was a gifted opportunity, which the Belgium 21-year-old seized with style.
Head coach Thiago Motta picked in-form striker Kolo Muani to lead the attack with 19-year-old Kenan Yildiz sitting behind the French international. Dusan Vlahovic was once again benched, although did make a late appearance.
Surprisingly loanee Muani was unable to score in his fourth outing since arriving from Paris Saint-Germain, having found the net in each of his three Serie A games for the Bianconeri.
Weston McKennie broke the deadlock on 34 minutes following a melee inside the box, powering the ball past ‘keeper Walter Benitez and into the top right corner.
With Muani man-marked out of the game, Motta shook things up after half-time with Mbangula replacing the largely ineffective Yildiz.
There was suddenly vast improvement from the hosts. Timothy Weah constantly raced down the right flank and sent in telling crosses for the strikeforce. But Muani and Mbangula were both thwarted early in the second half.
Former Inter Milan icon Ivan Persisic, who had been constantly jeered by Juve fans every time he touched the ball, had the last laugh by equalising on 56 minutes.
The 36-year-old Croatian international found the back of the net, but had to wait for a lengthy thumbs up from VAR to be awarded his first Champions League goal since 2020. There had been claims that winger Noah Lang had handled in the build-up to the strike.
Allianz Stadium was eerily silenced by this goal, as it was only PSV’s second shot on target. Juventus looked uneasy and on edge about letting the visitors back into the contest.
Motta needed to keep shuffling his pack in a desperate bid to secure a winner, and also try to loosen recent pressure on his shoulders.
Francisco Conceicao replaced Nicolas Gonzalez immediately after PSV had levelled matters. With skipper Manuel Locatelli and McKennie replaced by Khephren Thuram and Teun Koopmeiners respectively on 68 minutes.
These switches were still not enough to break down PSV’s resilience, so Vlahovic was sent on with 13 minutes to add some firepower in place of the neutralised Muani.
Motta’s gamble paid big dividends with the Turin titans pressing for a winner and Mbangula scoring within five minutes of exiled Dlahovic’s arrival.
Conceicao’s cross from the right was spilled by shotstopper Benitez and fell kindly into the path of Mbangula. He seized the opportunity with aplomb by sweeping the ball into the back of the net on the half volley.
The stadium erupted with joy and relief, while Motta broke into a rare smile. This was Juve’s second last-gasp success on the bounce, having scored a 2-1 Serie A triumph at Como courtesy of Muani’s 89th-minute penalty.
Motta enthused in the post-match press conference: “It was an even game against a team that wants to play good football and does it well.
“We are a young team that has to inject a lot of pace into the game in order to cause problems for teams.
“Dynamism is an important aspect of our game, we have to maintain a high level of intensity and we definitely have to improve on that.”
He praised Mbangula and McKennie, but there was no mention of outcast Vlahovic: “Once again the players who came off the bench raised the level of the team both in possession and out of possession.
“I'm very happy with Mbangula. He presses, he dribbles, he scores goals. He always has a fantastic attitude, he always gives everything.
“McKennie is a great player and an important figure in the group. He's a top player, and that's why he plays everywhere and often.”
And Motta fired off a warning shot: “This victory is only the first step, in the second leg we have to put in a great performance to progress to the Round of 16. “
Juventus welcome Inter Milan for Serie A action on Sunday, before they travel to Holland for next Wednesday’s Champions League second leg clash.