Mikel Arteta singled out Willian for "changing the game" against Benfica as Arsenal salvaged a dramatic victory to progress from Thursday's Europa League last-32 tie.
Arsenal, the designated home team, were on the brink of exiting the competition at the first knockout-stage hurdle for the second year running before a late turnaround on neutral soil in Greece.
Diogo Goncalves' impressive free-kick and Rafa Silva's finish into an empty net cancelled out Pierre-Emerick Aubameyang's opener to give Benfica a 3-2 aggregate lead.
Along with Thomas Partey, Willian was brought on two minutes later and the double change paid off as Arsenal hit back to salvage their campaign in the final half an hour.
Full-back Kieran Tierney lashed home and Aubameyang proved the match-winner three minutes from the end with a header to send Arsenal through 4-3 on aggregate.
Aubameyang took the plaudits with his late goal but Arteta felt Willian, who set up Tierney's goal, was the Gunners' real hero.
"Willian, specifically, I think he changed the game," Arteta said at his post-match news conference.
"He gave us much more composure in moments, produced some creativity, produced the goal for Kieran and we need everybody on board."
Willian completed 94 per cent of his 17 passes in the opposition half – the best return of any Arsenal player to have attempted at least three such passes.
The assist for Tierney's goal was the only key pass Willian played, with the Scotland international arrowing the ball away from Helton Leite at a crucial point in the tie.
Tierney, who became the first Scotsman to score for Arsenal in a major European competition since Willie Young against IFK Goteborg in March 1980 in the Cup Winners' Cup quarter-final, was also the recipient of individual praise from his manager.
"The way I'd describe him is all determination, all passion for what he does," the Spaniard said.
"The way he has come back from his injury and how willing he is to help the team. He gives us a big lift."
Aubameyang has now scored in seven of his last eight cup matches for Arsenal, netting 10 goals in total, with his only blank coming in the first leg against Benfica.
The Gabon international missed a big chance to send his side through at the same stage last season and is pleased to have put that miss against Olympiacos behind him.
"I definitely had that in my head but this is what gives me power every day to take the errors from the past and transform it to strength," he told BT Sport.
"The team showed a lot of character and we deserved the win. It was a hard game. What we showed tonight will be an example for the future."
Aubameyang now has 13 goals for the season in all competitions and Arteta added: "I completely trust him because we're producing the chances and you know when Auba has chances he's going to score goals."
Arsenal, who have now won on each of their last three visits to Greece, will learn their last-16 opponents in Friday's draw.