Roberto Di Matteo is set to return to Chelsea as No2 to André Villas-Boas when the Portuguese manager unveils his backroom staff on Wednesday morning. The Italian, who spent six years at Stamford Bridge as a player, is the Portuguese's surprise choice as his assistant.

Di Matteo has been out of work since his sacking as West Bromwich Albion manager in February. The 41-year-old was dismissed despite having led the West Midlands side back into the Premier League from the Championship at the first time of asking. The Italian has been on gardening leave since, but is now expected to return to football as Chelsea's No2 as Villas-Boas reshapes the coaching set-up at Stamford Bridge.

The Portuguese is bringing two compatriots, José Mario Rocha and Daniel Sousa, with him from Porto to act as his physical fitness coach and chief opposition scout respectively but his initial hopes of being joined by Vitor Pereira in London were dashed when his former assistant was appointed as his successor.

Di Matteo is best remembered at Stamford Bridge for scoring his side's opening goal, after only 42 seconds, in the 1997 FA Cup final against Middlesbrough,and he was also a scorer in the 1998 League Cup final against the same opponents and, in 2000, against Aston Villa in the FA Cup final at Wembley. He also won the European Cup Winners' Cup and Uefa Super Cup while at the club before a triple leg fracture suffered against the Swiss club St Gallen in a Uefa Cup tie in September 2000 forced his retirement from the game at the age of 30.

His appointment as a No2 is eye-catching given that Di Matteo's experience as a player and as a manager is arguably more extensive than that of Villas-Boas, although he has spent less time working in a domestic top flight.

He finished third in League One as manager of MK Dons in 2009 before taking over at West Bromwich Albion, with whom he finished second in the Championship a year later.

It remains to be seen whether another former Chelsea midfielder, Eddie Newton, who was Di Matteo's assistant at the Hawthorns and conducted much of the coaching during their time together at the club, will also return to old haunts as part of Villas-Boas's revamped coaching team. A vacancy has been created with the dismissal over the weekend of the assistant first-team coach, Paul Clement.

The Portuguese will be formally unveiled as the seventh manager of Roman Abramovich's eight-year ownership at Stamford Bridge on Wednesday morning and is expected to be flanked by his backroom staff. Significant squad strengthening is expected over the next few weeks – the players depart for a pre-season tour of east Asia on 17 July – with further changes still to be made behind the scenes. The Lille club doctor, Franck Le Gall, is expected to join Chelsea following the decision to release Bryan English over the weekend. English, like Clement and the fitness coach, Glen Driscoll, remains on gardening leave while compensation is negotiated.