Chelsea expect to complete the signing of Pedro from Barcelona within the next 24 hours after the Premier League champions triggered the £21.2m buy-out clause in the Spain forward’s contract and effectively beat Manchester United to his signature.

Pedro is due in London on Wednesday to undertake a medical and discuss personal terms, with United having withdrawn their interest. Their executive vice-chairman, Ed Woodward, had flown to Spain earlier this week to discuss the precise terms of his club’s offer, both to the winger and Barcelona, and a deal had appeared to be close – but United never actually moved to trigger the clause in his current contract.

Instead Louis van Gaal, having initially been inclined to secure Pedro, has drawn encouragement from the performances to date of his current squad and is understood to have sanctioned his club’s withdrawal from negotiations. Chelsea’s late emergence to challenge their interest appears to have forced their hand, with the player apparently convinced he should pursue his career at Stamford Bridge.

The Premier League champions – who recognise United as serious contenders for the title this season after a pristine start to the campaign – had come close to securing the 28-year-old World Cup and European Championship winner in January, only for José Mourinho to opt against pursuing a deal because Pedro was cup-tied in the Champions League.

Chelsea eventually signed Juan Cuadrado from Fiorentina instead, though the Colombian did not feature in the knockout tie against Paris Saint-Germain and has proved a huge disappointment since moving to England. He has effectively been made available for transfer, most likely on loan.

The deal for Pedro, which had been mooted again earlier this summer, will add significantly to Chelsea’s attacking options as the club endure their worst start to a domestic season since 1998. The winger has spent a decade at Camp Nou and has won 15 major trophies over his career at the Catalan club, only signing a contract extension through to 2019 in June, but he craved more game-time last season.

Chelsea are also weighing up whether to submit a fourth and final bid worth £40m to Everton for the England defender John Stones after seeing an offer of £30m knocked back on Tuesday. The owner, Roman Abramovich, will back Mourinho’s attempts to strengthen the squad before the closure of the window and has encouraged the recruitment department to secure the manager’s targets.