Manchester City are confident they have finally agreed a deal to sign Kevin De Bruyne from Wolfsburg for an initial €74m (£54m).

Negotiations over De Bruyne, the former Chelsea midfielder, have been taking place for several weeks and sources close to the Bundesliga club have confirmed that a breakthrough was reached on Wednesday. Several details still need to be resolved, including the structure of payments due and the player’s medical.

However, it is understood that De Bruyne will fly to England on Thursday for his medical and is expected to be officially unveiled as a City player on Friday.

If the deal, which could eventually be worth more than €80m (£58.5m) with performance-related bonuses, goes through, it would be the second highest transfer fee paid by an English club behind the £59.7m Manchester United paid for Ángel di María last summer. It would also surpass the club record £49m City paid to Liverpool for Raheem Sterling earlier this summer. De Bruyne is expected to be offered wages worth around £250,000 a week.

Despite widespread reports in Germany, however, De Bruyne’s agent, Patrick De Koster, refused to confirm any agreement had been struck, although he did hint that an announcement could be imminent. “I’m having dinner with Kevin at the moment but we have no news,” he said. “We are relaxed about the situation and we will see what happens in the next day or two. Kevin is not desperate to leave Wolfsburg but hopefully there will be a conclusion soon.”

Meanwhile Chelsea suffered a blow in their pursuit of the England defender Stones when Martínez confirmed Everton will not accept his request to leave and told the champions that “money can’t buy everything”. Chelsea’s third bid of £30m was rejected; a fourth of £40m is mooted.

“We have not rejected it yet because today was a match-day and that was our priority,” said Martínez after seeing his side beat Stones’s former club Barnsley 5-3 after extra-time in the Capital One Cup.

“We will reject it in the morning and get on with our business,” he added. “I am not surprised by the request because he is a young man who is under massive pressure from people and outside influences. What we need to do is give more value to contracts. We need to bring more seriousness to being part of a football club and to making sure that contracts are important.”