Ole Gunner Solskjaer saluted Manchester United's never-say-die star as they reached the Champions League quarter-finals with an historic 3-1 win over Paris Saint-Germain on Wednesday.
United became the first team in European Cup history to recover from losing the first leg of a knockout round tie 2-0 at home.
Romelu Lukaku scored twice either side of Juan Bernat's equaliser before Marcus Rashford converted a controversial stoppage time VAR-awarded penalty to send United through on away goals.
It was an incredible result given United were without the suspended Paul Pogba as well as nine injured stars including Anthony Martial, Jesse Lingard and Ander Herrera.
But United interim manager Solskjaer insisted he never doubted his players could do the unthinkable in the last 16 second leg in Paris.
"The belief in the boys was just what we hoped for. It was fantastic," Solskjaer told BT Sport.
Faced with a daunting first leg deficit, Solskjaer admitted United desperately needed Lukaku's second minute goal to put the momentum back in their favour.
Once United had opened the scoring, Solskjaer felt the French champions were haunted by the ghosts of their previous failures from winning positions in the Champions League, including blowing a 4-0 lead against Barcelona two years ago.
"It was a great start. We started with a plan to get the first goal, but we didn't expect it to come so soon," he said.
"We wanted an open game with many goals and that's what happened.
"There is always some mental doubt because they (PSG) have had those experiences.
"Our boys are young and fresh which gave us more energy when we needed that goal."
United had a huge slice of luck for the winner as VAR ruled that PSG defender Presnel Kimpembe, turning his back as he jumped, had handled a Diogo Dalot shot as it struck him on the arm in the penalty area.
Kimpembe barely extended his arm at all, but Rashford made the most of the opportunity as he calmly netted from the spot.
Solskjaer claimed it was the right decision, although he was nervous when Rashford stepped up to take his first ever penalty for United.
"The referee had a big, big call to make. My staff said the player made himself big, so it's a clear penalty," Solskjaer added.
"I was in the Champions League with Molde and we got a penalty in the last minute and my player missed that and we went out.
"I had to try and calm everyone down. Of course there were doubts. But Rashford, he's 21 and the pressure on the boy, there were no nerves whatsoever, fearless."
Solskjaer has had an astonishing impact since arriving from Molde to replace the sacked Jose Mourinho in December.
He is yet to lose a domestic match and has won every away game in all competitions.
After masterminding one of the great European comebacks it is impossible to think he won't get the job on a permanent basis.
When asked about the prospect of taking charge full-time, the Norwegian said: "Until the summer, let's see what happens."
England striker Rashford insisted he never felt even a second of concern as he endured the long wait to take the penalty while VAR looked at the incident.
"I think it was just about keeping a cool head. That's what you practice for. I wanted to take it," he said.
"Those moments are the moments we live for, and we want to come out of them smiling after.
"It's a beautiful thing, to have 10 players injured too, but it's an opportunity and it's what we deserve."
VAR to Porto's rescue
Alex Telles converted a VAR-awarded penalty deep into extra time as Porto defeated Roma 3-1 on Wednesday to reach the Champions League quarter-finals following a tense 4-3 win on aggregate.
Francisco Soares nudged Porto ahead with a simple tap-in on 26 minutes, but Daniele De Rossi equalised from the spot before half-time after Eder Militao chopped down Diego Perotti.
Moussa Marega restored the lead on the night for Porto early in the second half to level the tie as he struck in his sixth successive appearance in Europe.
An additional half-hour was required to settle an encounter that looked to be heading for a shootout before Telles tucked home from the spot on 117 minutes after a tug on Fernando by Alessandro Florenzi was spotted upon review.
"It was not just me that scored the penalty, it was the whole team. The Dragao, the full stadium, made me feel at ease. It was a very good energy," said Telles.
"We've got to accept it, even if the way it happened is terrible to accept," Roma captain De Rossi told Sky Sport Italia.
Porto coach Sergio Conceicao, a former player at Roma's city rivals Lazio, had expressed the need for patience as his side set about attempting to retrieve a 2-1 deficit.
Yet they threatened twice inside the opening 10 minutes at the Estadio do Dragao as Jesus Corona hammered a volley narrowly over, with Telles lashing into the side-netting from a tough angle.
Corona again tried his luck from range, his shot again dipping over the top, and the Mexico winger was once more involved as Soares poked in the opening goal.
Marega, back in the side after missing the first leg with a thigh injury, pinched the ball from Kostas Manolas and was then picked out by Corona on the overlap to square for Soares to slot home.
Porto's lead lasted barely 10 minutes as Militao lunged in on Argentine Perotti, with De Rossi coolly rolling his penalty past three-time Champions League winner Iker Casillas.
Marega catches Messi
Porto captain Hector Herrera, who was booked and will miss the quarter-final first leg, tested Robin Olsen with a bending effort just before the break when Roma lost skipper De Rossi following a crunching tackle by Danilo.
Soares should have netted a second when his downward header skipped off the ground and flashed over the bar, while Olsen produced a superb fingertip save to claw out a Marega strike.
Olsen was powerless to stop France-born Mali international moments later though as Marega timed his run perfectly to volley Corona's curling cross into the roof of the net.
Marega is now level with Lionel Messi and Dusan Tadic with six goals in this season's tournament -- and trails only Robert Lewandowski (eight).
Pepe and Edin Dzeko were both booked following a theatrical clash near midfield, a caution that also rules the Portuguese defender out of his side's next match in the competition.
A dreadful Pepe error presented Perotti with an opportunity he failed to exploit as Roma searched for a late goal, while Otavio tested Olsen from distance towards the end of the 90 minutes.
Marega went agonisingly close to scoring again early in extra time, while Dzeko dinked the ball over Casillas only for Pepe to race back and clear off the line in desperation.
With penalties seemingly on the horizon, Porto grabbed a dramatic winner after Turkish referee Cuneyt Cakir pointed to the spot upon reviewing an incident in which Florenzi hauled back Fernando as the substitute stretched to reach a driven low cross.
Telles sent Olsen the wrong way to fire Porto into their first quarter-final since 2014-15, although the hosts faced an anxious wait after Patrik Schick tumbled to the ground in the area before Cakir ruled there was no foul.