Belgium star Romelu Lukaku will miss the Nations League clash with Poland due to injury as Roberto Martinez implored his side to respond from defeat to Netherlands.
Martinez's side are ranked second in the world but were thoroughly outplayed on Friday as Netherlands cruised to a 4-1 victory.
Lukaku limped off in the first half with the scores level, before goals from Steven Bergwijn, Denzel Dumfries and Memphis Depay secured Netherlands' first win on Belgian turf since 1997.
Martinez assured the issue with Lukaku was simply "a knock" after the game, but Belgium confirmed on Monday that the Chelsea striker will be absent for the clash with Poland on Wednesday.
The Red Devils added Lukaku has started treatment, leaving it unclear whether he will be fit to feature for the remaining clashes in June against Wales and the reverse fixture with Poland.
While Martinez may be without his talisman as Belgium ramp up their World Cup preparations for Qatar, the Red Devils coach urged his team to respond against Poland.
"[The Netherlands defeat] reminded us of the level we have to reach for the World Cup," he told reporters.
"This type of tough game will help us improve. We don't like to lose but we'll learn. It's an ongoing process, and the next test will come quickly against Poland."
The defeat to Netherland was also the first time Belgium had lost on home soil against any side since September 2017, while it was the first time the Red Devils had conceded four goals at home since October 2010.
Poland visit Brussels in the next League A Group 4 fixture and coach Czeslaw Michniewicz expects Belgium to come out fighting for a response.
"The Netherlands [won 4-1 in] Belgium, but both teams could have scored more; the Belgians had a lot of chances, plenty of set-pieces," Michniewicz said.
"We will have an interesting meeting with a team that has many classy individuals. Belgium will be motivated after such a heavy defeat."