Aitor Karanka warned his Middlesbrough side that Saturday's opponents Tottenham will not be weakened by the loss of England striker Harry Kane.
Kane topped the Premier League goalscoring charts last season and had scored in his past two league appearances for Spurs after making a slow start to the campaign.
However, the 23-year-old damaged ligaments in his right ankle in last weekend's 1-0 victory over Sunderland and no timeframe has been put on a return.
Karanka, though, is wary of the strength of Tottenham's squad with Vincent Janssen - who scored his first Spurs goal in a 5-0 EFL Cup win over Gillingham on Wednesday - likely to deputise.
"They have top players and we have to know one mistake in the Premier League and we will be punished," the Boro manager told a news conference ahead of the contest at the Riverside Stadium.
"In the Championship you can be lost for 10 minutes and nothing happens, but now 10 minutes lost on the pitch is three goals.
"I think we would miss Alvaro [Negredo] more than they will miss Kane. They have other players to play, an amazing squad. Mauricio [Pochettino] will play someone who is really motivated."
Karanka also addressed reports that Boro's 23-year-old centre-back Ben Gibson is line for a call up to the England senior team.
"He's a player who's played the last two and a half years and has improved," added the ex-Real Madrid assistant.
"If one day he went to the national team it would be amazing for him and the club, he's part of this club, but now he's here and has to think about winning games.
"Of course [you will learn] when you have players around you as good as [England have], I've experienced in my career when you're surrounded with players like that you improve.
"But now he is [already] with [Daniel] Ayala and Bernardo [Espinosa] and [Calum] Chambers."