Ruben Amorim admitted that Manchester United struggled to adapt to his tactics during a hard-fought 1-1 draw against Ipswich Town at Portman Road.
The new manager's debut saw flashes of promise but also highlighted areas for improvement.
United struck early through Marcus Rashford, who netted within 80 seconds following a surging run and cross from Amad Diallo, deployed as a right wing-back in Amorim's evolving 3-4-3 system.
However, Ipswich equalised before half-time when Omari Hutchinson's deflected long-range strike left Andre Onana helpless.
In the second half, Ipswich looked the stronger side, repeatedly testing United's defence. Onana was pivotal in preserving the draw, making several critical saves, including a stunning point-blank denial of Liam Delap.
Amorim's tactical adjustments included playing Noussair Mazraoui in an unexpected centre-back role.
While versatile - having played as a right-back, left-back, and even in attacking midfield during a Europa League draw against Porto - Mazraoui's future in the back three remains uncertain with Lisandro Martínez, Leny Yoro, and Harry Maguire sidelined through injury but expected to return.
Amorim praised Mazraoui as "crucial" to his plans but acknowledged the experimental nature of his team selection.
"It was really hard for them [the players, adapting to the new formation]. They were thinking what to do. It was not fluid, which is normal after just two training sessions, but they tried hard," Amorim told BBC.
"They have so much space to improve. I am really happy because they tried but they can do so much better.
"We don't have too many centre-backs so we have to adapt some players. I thought Noussair Mazraoui did really well.
"He is so smart and is so important for us. He can play anywhere and that kind of player is crucial for our future."
