Marco Silva admitted Theo Walcott's early withdrawal from Everton's defeat to Manchester City disrupted a pre-determined game-plan against the champions.
Walcott was struck in the head by a Raheem Sterling delivery in the first minute of the game and eventually left the field on a stretcher.
Silva offered a positive post-match assessment of the 30-year-old former Arsenal winger who was immediately discharged from hospital, meeting team-mates in the dressing room following the loss.
Walcott's inclusion in Everton's starting XI had initially raised eyebrows but the manager confirmed his presence was to exploit a weakness identified in City's left-side.
"It's true," Silva replied when asked if the injury was a blow to his initial tactics.
"You know always something can happen. We had a plan with him to explore the space we know they will give us behind them and behind [Oleksandr] Zinchenko or [Benjamin] Mendy, we did not know which [left-back] would play.
"We thought with Theo Walcott we could explore something with that but unfortunately he came off so early. Alex [Iwobi] started well and did well and we changed Richarlison to the right side.
"But of course, it's never good when you have a plan and prepare something for the game and the first one or two minutes we have to change something."
