Arsenal manager Mikel Arteta took a gamble on converted left-back Myles Lewis-Skelly in a midfield role for Tuesday's Champions League semifinal second leg against Atletico Madrid.
Arteta, whose side are level at 1-1 after the first leg, had used Lewis-Skelly in central midfield for the first time in his career during Saturday's 3-0 win against Fulham in the Premier League.
With a place in the Champions League final against Paris Saint-Germain or Bayern Munich up for grabs, Arteta was expected to revert to Martin Zubimendi in the position alongside Declan Rice.
But the Spanish boss named an unchanged team, leaving Zubimendi and club captain Martin Odegaard on the bench in favour of the 19-year-old Lewis-Skelly.
Arteta started with Viktor Gyokeres as his striker, with Bukayo Saka and Leandro Trossard on the flanks and Eberechi Eze in the advanced midfield role.
Atletico boss Diego Simeone recalled his stars after making a host of changes for Saturday's win at Valencia as he rested his key players for the decisive trip to north London.
Julian Alvarez was back up front for Atletico, alongside French veteran Antoine Griezmann.
Arsenal reached their only Champions League final in 2006, while Atletico last appeared in the final in 2016.
Neither club has ever won the Champions League.
STARTING LINE-UPS
Arsenal (4-2-3-1)
David Raya; Ben White, William Saliba, Gabriel Magalhaes, Riccardo Calafiori; Declan Rice, Myles Lewis-Skelly; Bukayo Saka (capt), Eberechi Eze, Leandro Trossard; Viktor Gyokeres
Coach: Mikel Arteta (ESP)
Atletico Madrid (4-4-2)
Jan Oblak; Marc Pubill, Robin Le Normand, David Hancko, Matteo Ruggeri; Giuliano Simeone, Marcos Llorente, Koke (capt), Ademola Lookman; Antoine Griezmann, Julian Alvarez
Coach: Diego Simeone (ARG)
Referee: Daniel Siebert (GER)