Antonio Conte has thrown down the gauntlet to Diego Costa on the eve of Chelsea’s Premier League season opener at home to West Ham United on Monday night, telling him to concentrate on playing as a penalty box finisher and to score 30 goals.

The new manager, who is keyed up and in his own words “not relaxed” before his first competitive game with the club, was asked whether he would set Costa the target of 20 goals for the season. “Why 20 and not 30?” he shot back, with a smile.

Conte qualified the remark by saying that he never gives his strikers specific goal targets but the ambition was clear; he wants Costa to aim high and put his heart and soul into the collective effort. Costa, who arrived from Atlético Madrid in 2014, scored 20 league goals in his first season as Chelsea won the title. But he managed only 12 in the competition last time out, in what was a testing campaign.

The 27-year-old felt his goal touch evaporate as the club imploded under José Mourinho and, having been left out of the team, an example of his frustration came when he threw his training bib in the direction of Mourinho, after he was left as an unused substitute at Tottenham Hotspur on 29 November.

Costa’s form improved dramatically after Guus Hiddink took over as the caretaker manager following Mourinho’s sacking in mid-December but he was not selected by Spain for the Euro 2016 finals and has endured a summer of speculation over his future.

Atlético made no secret of their desire to re-sign him and Chelsea even threatened to take action against the Spanish club in two written warnings. But Costa has stayed at Stamford Bridge, and it sounded as though Conte wanted to send him a message.

“Diego is a forward and he knows that, in my idea of football, the forward must be a point of reference for the team,” Conte said. “I don’t like that a forward moves around the pitch. I like him to stay there [in the box] because you are a forward and your commitment is to score goals and to stay in the right position. You are a forward – not a midfielder, not a defender.

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“I don’t like to speak about single players but I will make an exception. Diego is a great player. I know that he is a fantastic finisher but I think he can still improve a lot. I hope for this. I try to improve all of my players. Their past is not important to me and now, I am seeing a good attitude from Diego – to work and to improve in different situations.

“I am happy that Diego stays here to work with us. We know that we can improve through the work and the most important thing is that the players have put themselves into this idea. Diego can give a lot to this team and I am sure he will have a good season.”

Conte’s passion and work ethic has underpinned everything he has done in the game. He said it was why he was able to remain as a player at Juventus for 13 years and also coach the club for three years and the Italy team for two years. It is what has carried him to Stamford Bridge. Costa, too, is known as a fiery competitor and Conte said he likes his spirit.

“Diego always shows a great passion and I am the same,” Conte said. “He doesn’t want to lose. I like this passion and I want to put it in the team. It’s important to have passion for your work, for your football. It can help you to get over difficulties. I like this commitment – that the players work very strongly for the team.

“I ask Diego for this and I demand this of him. I never ask [specific goal targets] of my strikers but I ask Diego and all the players to have a great attitude. Then, the goals arrive. I am sure of this. It’s important that the players play our football, not their own football.”